List of all talks

ROW = 242
num_talk =
[264] Topic: Source apportionment of black carbon

Speaker: Dr U C Dumka
Affiliation: ARIES
Date (yyyy-mm-dd): 2017-06-27
Time: 15:30hr
Venue: Auditorium

Abstract: The current presentation divided into two parts: Part-1: Air Pollution and BC source apportionment in Delhi region during a winter research campaign This deals with the temporal variation of BC and air pollutions. The special focus is given on the source apportionment of BC and evaluation of the contribution of fossil fuel and wood burning on the black carbon. Part-2: Fossil fuel and wood burning contribution to BC during winter: Influence of meteorology and boundary layer dynamics The second parts deal with the source identification of BC and role of meteorology and boundary layer dynamics.


About Speaker: Scientist at ARIES, Nainital



[263] Topic: Statistics in X-ray spectral analysis

Speaker: Bharti Arora
Affiliation: ARIES, Nainital
Date (yyyy-mm-dd): 2017-06-20
Time: 16:15hr
Venue: Auditorium

Abstract: Statistics are needed at every step of a scientific analysis. Statistics allow us to make decisions, evaluate observations, models, formulate questions and proceed forward with further investigations. The main goal of X-ray data analysis is to learn more about the physical properties of a source. When the new data arrives, statistics are employed to quantify the measurements. Typically, a parameterized approach to model the data is taken wherein physical models with certain parameters (e.g. temperature and density of a hot medium emitting X-rays) are applied to the data. Finding and evaluating a model that best describes the observed data will be the focus of my talk.


About Speaker: JRF at ARIES



[262] Topic: Young stellar objects : tool to understand star formation process

Speaker: Rakesh Pandey
Affiliation: ARIES, Nainital
Date (yyyy-mm-dd): 2017-06-20
Time: 15:30hr
Venue: Auditorium

Abstract: The process of star formation constitutes one of the main problems of modern astrophysics. As compared to stellar evolution it is very ill understood problem. Young stellar object (YSO) denotes a star in its early stage of evolution. Census of young stellar objects (YSO), correlation of their physical properties with ionizing source/s and their spatial distribution in a molecular cloud, are some of the signatures used to study the time-scale and star formation processes in a given region. In this talk I will talk about the various kind of star formation mechanisms, particularly focusing on the star formation on the edge of HII regions, a brief introduction about the YSOs. I will conclude my talk with, how studying YSOs helps us to understand star formation process.


About Speaker: JRF at ARIES



[261] Topic: Pre-main sequence evolution of low mass stars

Speaker: Tirthendu Sinha
Affiliation: ARIES, Nainital
Date (yyyy-mm-dd): 2016-06-14
Time: 15:30hr
Venue: Auditorium

Abstract: Stars go through different processes during their pre-main sequence evolution. Stellar parameters like radius, temperature, density etc. suffer drastic changes in different stages. Molecular clouds of few thousand astronomical unit(AU) contract to form stars of the size of fraction of AU whereas the temperature rises from 10-50 K to the order of 10^6 K and density increases ~10^20 times. I will mainly discuss different mechanisms that drive the process of contraction and finally forms a main sequence star.


About Speaker: JRF at ARIES



[260] Topic: Comets - a prob to explore early solar nebula

Speaker: Prof. U. C. Joshi
Affiliation: Physical Research Laboratory, Ahmedabad
Date (yyyy-mm-dd): 2017-05-25
Time: 15:30hr
Venue: ARIES, Auditorium

Abstract: Cometary bodies are located in the farthest region of the solar system, hence least weathered and thus possess pristine material. At some instance these bodies are deected toward the inner region of solar system and make glorious appearance in the sky. Cometary material is mixture of dust and ices and the physical conditions and chemical composition of early solar nebula in imprinted on it. On approaching closer to the Sun ices get sublimated and ejected out of the nucleus forming coma. Remote observations from ground based observatories allow us to study the constituents of the coma. Study of cometary dust and gas is of great importance to investigate physical conditions and chemical make up that existed in the beginning of the formation of solar system. The talk will cover a brief introduction and importance of comets and some of the recent results will be discussed.


About Speaker: Visiting Professor



[258] Topic: “Trappist – 1 Planetary System“

Speaker: Master Sajal Kumar (Gwalior), Master Kshitij Samdani (Neemu
Affiliation: Aryabhat Foundation, Bhopal
Date (yyyy-mm-dd): 2017-05-18
Time: 11:30hr
Venue: ARIES Auditorium

Abstract: The newly discovered Red Dwarf Star Trappist-1a is nearly 40 light years away from us. This Red Dwarf has Seven planets going around it which are quite similar in size to our planet Earth. Human anxiety that whether we are just alone in this grand Universe has budded up the possibility of having some life form or other on any of these planets. This fact has driven a lot of public concern over this system. PS: All are inviated to this talk. The students will also display a solar telscope starting around 11:00am. It is reccomended to encourage these students while interacting. The presentation evaluates several aspects about how and why this planetary system would be so fit to be hosting life forms. The students try to evaluate some basic questions related to this subject from their point of view. They would discuss the contribution of various missions in this sector. They also suggest some innovative steps to be taken in further search for extra terrestrial intelligence. In my absence on 18th, Dr. Hum chand will co-rodinate the program.


About Speaker: Master Sajal Kumar (Gwalior), Master Kshitij Samdani (Neemuch) and Master Chinmay Jindal (Kishangarh) from Aryabhat Foundation, Bhopal. It may please be noted that these students have been selected out of a tough two tier test conducted in MP.



[257] Topic: LAXPC instrument : Its overview and the science that can be done

Speaker: Shilpa Sarkar
Affiliation: ARIES, Nainital
Date (yyyy-mm-dd): 2017-05-16
Time: 15:30hr
Venue: Auditorium

Abstract: LAXPC instrument : Its overview and the science that can be done ASTROSAT is India’s first dedicated multi-wavelength space satellite. It observes the universe in the optical, UV and X-rays ranging from soft to hard. One of the major payloads onboard ASTROSAT is LAXPC (Large Area X-ray Proportional Counter) which is mainly devoted to X-ray timing and spectral studies of astronomical objects having energy in the range 3-80 keV. This talk will have a brief overview of the instrument and the science that can be done with it.


About Speaker: Junior Research Fellow



[256] Topic: Variable stars and variability in open star clusters.

Speaker: Jayanand Maurya
Affiliation: ARIES, Manora Peak, Nainital
Date (yyyy-mm-dd): 2017-05-09
Time: 15:30hr
Venue: Auditorium

Abstract: A variable star is a star whose apparent brightness changes over a period of time. In this talk I will briefly discuss different types of variable stars and reasons for variability. A brief discussion on why to study variability in open star clusters and distance measurement using variable star.


About Speaker: JRF at ARIES



[255] Topic: Satellite Remote Sensing of Fires

Speaker: Prof Christopher Justice
Affiliation: University of Maryland
Date (yyyy-mm-dd): 2017-05-08
Time: 09:30hr
Venue: Ashwini Council Room

Abstract: A general overview of satellite product with a specific interest on the NASA Moderate Imaging Spectroradiometer (MODIS) data product will be presented. Detailed discussion will be made on the MODIS fire product.


About Speaker: Prof Christopher Justice is a Professor and Dept. Chairman of Geography at the University of Maryland. Currently, Prof. Justice is a Program Scientist for NASA Land Cover Land Use Change (LCLUC) Program. Most recently, he became the Co-Director for the Center for Global Agricultural Monitoring Research. Current research of Prof Justice is on land cover and land use change, the extent and impacts of global fire, global agricultural monitoring, and their associated information technology and decision support systems. Prof Justice received his Ph.D. from the University of Reading, United Kingdom, in 1977.



[254] Topic: KOI HAI ? BRAHMAAND MEIN JEEVAN (Is anyone? Life in the Universe)

Speaker: Dr. C. M. Nautiyal
Affiliation: At present:Chairman, young Scientists Project scheme, UP govt., Retd. Scientist:
Date (yyyy-mm-dd): 2017-05-01
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: Life began on Earth 3.8 billion years ago as a consequence of many coincidences of astronomical, chemical and circumstantial nature. Having taken off from a simple single form of life, it has reached the present complexity of human mind that strives to explore extra-terrestrial abodes of life. In the universe comprising of trillions of galaxies, each of hundreds of billions or more stars,it doesnt appear logical to believe that Earth is the only cradle of life. But the truth remains that we have not seen any evidence of extra-terrestrial life. In this popular level talk, an attempt will be made to explore proper abodes of life outside Earth. Organic material in meteorites, strange bacteria in the depths of Mediterranean Sea and survival of life in unexpected places of extreme conditions seem to shatter our concept about normal life. The results from the recent planetary missions of NASA, ESA and other countries indicate that we may be on the brink of discovery of something new.


About Speaker: At present, he is Chairman, Young Scientists’ project scheme of UP Govt.; Member, Board of Studies, CCS Meerut University; and continuing as coordinator of the Rock Art Documentation Committee for UP and the outstation member of Vigyan Parishad, Prayag. Formerly, Scientist-F, at BSIP (DST) Lucknow.



[253] Topic: Unveiling new population of Active Galactic Nuclei using deep multi-wavelength surveys

Speaker: Dr. Veeresh Singh
Affiliation: PRL, Ahmedabad
Date (yyyy-mm-dd): 2017-05-31
Time: 15:30hr
Venue: ARIES, auditorium

Abstract: Active Galactic Nuclei (AGN) studies have mainly been limited to the local Universe, but more sensitive observations in recent years allow us to unveil new population of AGN at distant Universe. Using our deep radio continuum surveys combined with auxiliary optical, IR surveys we discover a new population of AGN called--Infrared-Faint Radio Sources (IFRSs). These AGN are at the redshift of (z) ~ 2 – 4 and exhibit diverse properties in terms of their radio luminosities, sizes and spectra, indicating them to be radio-loud AGN at different evolutionary phases. The optical-to-MIR colors and their non-detection in the X-ray band suggest them to be AGN hosted in dusty-obscured-galaxies. The discovery of IFRSs has important implication on the models of galaxy evolution and in explaining the missing unresolved AGN population predicted by the Cosmic X-ray Background model. In this talk I shall also discuss the role of deeper surveys from telescopes operating at radio, optical, IR and X-ray wavelengths.


About Speaker: Dr. Veeresh Singh is faculty in Astronomy and Astrophysics Division of Physical Research Laboratory Ahmedabad. His research interest involves: (i) Multiwavelength study of Active Galactic Nuclei (AGN) (ii) Formation and evolution of AGN and their host galaxies (iii) Population of AGN at high-redshifts and their environments and (iv) Deep radio and ancillary surveys of extragalactic fields.



[252] Topic: Active Galactic nuclei: tool to probe the high-redshift Universe

Speaker: Priyanka Jalan
Affiliation: ARIES, Manora Peak, Nainital
Date (yyyy-mm-dd): 2017-04-25
Time: 15:30hr
Venue: Auditorium

Abstract: Active Galactic nuclei (AGNs) refers to the existence of energetic phenomena in the nuclei or central regions, of galaxies which cannot be directed to stars. In this talk, I will explain the factors which helps in distinguishing AGNs from stars and what lead to the Unification model of AGN. A brief overview of the optical spectrum of AGN will also be given. Finally, I will conclude with why are we interested to study such distant objects.


About Speaker: JRF at ARIES



[251] Topic: Counting photons in the Universe: from extreme UV to far-IR

Speaker: Dr. Vikram Khaire
Affiliation: NCRA
Date (yyyy-mm-dd): 2017-04-27
Time: 15:30hr
Venue: ARIES auditorium

Abstract: The photons emitted by galaxies (from stars and accreting super-massive blackholes) generate an uniform background know as the extragalactic background light (EBL). The spectrum of EBL is an important quantity for studying several astrophysical problems. For example, in extreme UV regime, the EBL is essential to study the hydrogen and helium reionization, metal enrichment and thermal history of the intergalactic medium, and missing baryons at low-redshift. In optical to far-IR regime, the EBL gives insight into the propagation of the high-energy gamma rays emitted by distant sources. In this talk, speaker will discuss how to count photons and estimate the spectrum of the EBL, especially the theoretical and observational intricacies involved in it. Also, he will introduce the state-of-the-art EBL model and its applications to wide range of problems.


About Speaker: Dr. Khaire is visiting fellow at NCRA, and did his Ph.D from IUCAA. His research interest is: Intergalactic medium, Extragalactic background light, Hydrogen and helium reionization, Star formation history.



[250] Topic: 21-cm Cosmology

Speaker: Prof. Somnath Bharadwaj
Affiliation: IIT Kharagpur
Date (yyyy-mm-dd): 2017-05-15
Time: 15:30hr
Venue: ARIES auditorium

Abstract: The redshifted 21-cm cm line from neutral Hydrogen provides an unique tool for studying the Universe. This radiation appears as a faint background in low frequency radio observations and the measurement of the fluctuations in this background radiation potentially allow us to study the large scale structures in Universe over a very broad range of redshifts. The measurement of this radiation also hold the potential of allowing us to probe the formation of the first galaxies which are believed to have re-ionised the universe. This talk will start with a broad overview of this topic and then present some of the recent research.


About Speaker: Somnath Bharadwaj is Professor of Physics at IIT Kharagpur. His group work in the areas of Astrophysics and Cosmology. His research is currently focused on using low frequency radio telescopes to study the high redshift universe using the redshifted 21-cm radiation from neutral hydrogen. Group is involved in theoretical, computational and also on observational work connected to this issue. (see Prof. Somnath on-line detail pedagogical lecture in astronomy at: http://www.nptelvideos.in/2012/11/ especially on astrophysics & cosmology , also available on utube)



[249] Topic: A new Catalog of Narrow Line Seyfert 1 Galaxies from the Sloan Digital Sky Survey Data Release 12

Speaker: Hum Chand
Affiliation: ARIES
Date (yyyy-mm-dd): 2017-04-03
Time: 15:30hr
Venue: ARIES auditorium

Abstract: The talk will focus in general on AGN and particularly on the narrow-line Seyfert 1 (NLSy1) galaxies. On NLSY1, I shell focus on our recent new catalog we prepared using the Sloan Digital Sky Survey Data Release 12 (SDSS DR12) by carrying out systematic analysis through modeling of the host galaxy, AGN continuum and prominent emission lines of the spectra of all the 68,859 SDSS DR12 objects that are classified as QSO by the SDSS spectroscopic pipeline with z lt 0.8. Our new catalog contains a total of 11,101 objects which is about 5 times larger than the previously known NLSy1 galaxies till date. Their monochromatic luminosity at 5100AA is found to be strongly correlated with H-alpha, H-beta and [O III] luminosities. The optical Fe II strength in NLSy1 galaxies is about two times larger than the broad-line Seyfert 1 (BLSy1) galaxies. Their cross correlation with Radio(FIRST) and X-ray catalog, as well as impact of this new enlarged catalog for future AGN studies along with the key NLSY1 parameter and parameters cross-correlations will also be discussed. The full catalog will be available on line from APJS catalog pages in future, with all the extracted parameters.


About Speaker: Scientist ARIES



[248] Topic: Evolution of magnetic activities in late-type stars

Speaker: Mr. Subhajeet Karmakar
Affiliation: ARIES
Date (yyyy-mm-dd): 2017-03-31
Time: 10:15hr
Venue: Auditorium

Abstract: Cool stars with convective outer envelope show similar-type of magnetic activities to that of the Sun hence have a similar type of dynamo. Although, the observations of these stars have introduced a range of stellar rotation periods, gravities, masses, and ages, which put into the debate on the magnetic dynamo. The important observational evidences of these magnetic activities are the presence of dark spots on the surface, short- and long-term variations in spot-cycles, and flares. In this thesis, we have chosen five active stars with luminosity class V to III to investigate the evolution of magnetic activities. These active stars are LO Peg, 47 Cas, AB Dor, CC Eri and SZ Psc. Using ~24 yrs long multi-band data, we found that the surface of LO Peg rotates differentially showing solar-like SDR pattern with a period of ~2.7 yr. The surface coverage of cool spots is found to be in the range of ~9--26 % in LO Peg. Several moderate-sized flares and two superflares on active dwarfs 47 Cas, AB Dor, and CC Eri are also analyzed. A large flare on evolved RS CVn type stars was also observed and analyzed. The time-resolved spectral analysis during these flares shows the variation in the coronal temperature, emission measure, and abundances. The peak temperatures in these moderate flares are found to be in the range 10--90 MK, whereas the peak flare temperatures in superflares are found to be mode than 120 MK. In most flares, during the decay, a sustained heating was detected. Using the hydrodynamic loop modeling, we derive loop-lengths of the flares of the order of 10^10 cm. In nutshell, we found that the magnetic activities in these star changes with time.


About Speaker: Mr. Subhajeet Karmakar is a research scholar and pursuing PhD under supervision of Dr Jeewan Pandey. This is his PhD submission presentation.



[247] Topic: Cold Gas at High Redshift

Speaker: Nissim Kanekar
Affiliation: NCRA-TIFR
Date (yyyy-mm-dd): 2017-03-27
Time: 15:30hr
Venue: Auditorium

Abstract: The gas and dynamical masses of damped Lyman-alpha absorbers (DLAs) have been open questions in the field of galaxy evolution for more than three decades. This talk will describe new results from Arecibo and ALMA searches for HI 21cm, CO and CII-158 micron searches emission from a sample of DLAs at, respectively, low (z < 0.1), intermediate (z~0.7) and high (z~4) redshifts. Our HI 21cm observations of the DLAs at z<0.1 yield normal gas masses, <~ 5 x 10^9 solar masses, but very high gas-to-stars mass ratios, ~ 5-100, far higher than in normal galaxies. For the absorbers at intermediate redshifts, we obtain large molecular gas masses in the six systems with CO detections, despite their low optical star formation rates. We also obtain high star formation rates (based on dust continuum emission) and high CII-158 micron line luminosities for the DLA host galaxies at z~4. For the CO and CII-158 micron detections, the impact parameters of the host galaxies are high, 15-45 kpc, far larger than expected based on earlier studies. These are the first CO and CII-158 micron detections in DLA hosts, providing a new window on physical conditions in the absorbers and yielding a new tool to identify DLA host galaxies at high redshifts.


About Speaker: Dr. Nissim Kanekar is a faculty with NCRA-TIFR



[246] Topic: Short period variable stars in young open cluster Stock 8

Speaker: Sneh Lata
Affiliation: ARIES
Date (yyyy-mm-dd): 2017-03-10
Time: 11:30hr
Venue: ARIES Auditorium

Abstract: Time series photometry of 49 short period variable stars in the cluster Stock 8 is presented. Thirteen main-sequence and 16 pre-main-sequence stars are found to be probable members of the cluster. The main-sequence stars are classified as slowly pulsating B stars, beta Cep and delta Scuti stars. Six main-sequence stars may belong to new class variables as discussed by Mowlavi et al. (2013) and Lata et al. (2014). The age and mass of identified pre-main-sequence stars are found to be < 5 Myr and in the range of 0.5


About Speaker: Paper presentation



[245] Topic: High Power VHF Radar Studies of Earth Atmosphere and Ionosphere

Speaker: Prof P B Rao
Affiliation: National Remote Sensing Centre
Date (yyyy-mm-dd): 2017-02-20
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: High power phase coherent radars at VHF opened up opportunities to explore the earth’s atmosphere and ionosphere with unprecedented spatial and temporal resolutions. The application of the 50 MHz Jicamarca radar, built originally for coherent and incoherent backscatter studies of the ionosphere, to probe the structure and dynamics of the middle atmosphere has led to what is now referred to as MST (Mesosphere-Stratosphere-Troposphere) radar technique. The basic theory for the high power VHF radar backscatter mechanisms, radar technique, signal and data processing methods for parameter retrieval and an overview of the scientific results from high resolution studies of atmospheric structure and dynamics and ionospheric plasma irregularities carried out using MST radar at Gadanki are presented.


About Speaker: Prof P B Rao is an renowned expert in the field of high power VHF radars. Earlier, he served as a Director, National atmospheric research laboratory during 1990-1998. Prof Rao is presently serving as visiting professor (Honorary) in National remote sensing centre, Dept. of Space, Hyderabad.



[244] Topic: Study of Galactic Star Forming Regions and Related Instrumentation

Speaker: Neha Sharma
Affiliation: ARIES
Date (yyyy-mm-dd): 2017-01-20
Time: 15:00hr
Venue: ARIES Auditorium

Abstract: The nearby isolated molecular clouds are the compelling laboratories to study the evolution of globules and the various processes of star formation. Magnetic field plays a crucial role in the evolution of these molecular clouds as well as it affects the star formation processes. Hence a comprehensive study of magnetic field towards these molecular clouds is required to understand these processes. In this thesis, we have studied the magnetic field geometry and strength in various environments of molecular clouds e.g., cloud-cloud collision scenario, bright-rimmed clouds (BRCs), high-latitude clouds etc. When unpolarized starlight passes through the intervening interstellar dust grains that are aligned with their short-axis parallel to the local magnetic field, it gets linearly polarized. The plane-of-the-sky magnetic field component can, therefore, be traced by doing linear polarization measurements of background stars projected on the clouds. We have chosen the regions to map magnetic field geometry on the basis of two different classifications of star formation, triggered and spontaneous. Triggered star forming regions e.g. cometary globules, bright-rimmed clouds are mainly associated with HII regions having a high mass star in the center of it. When massive star forms it photoionizes the surroundings, forming HII regions, that display highly irregular structures such as filaments, pillars, CGs and BRCs. In the radiation-driven implosion (RDI) mode of triggered star formation, the incoming ionizing radiation from that massive star further compresses these small clouds to collapse and make them gravitational unstable to form new stars. We have chosen a HII region Sh2-262 having multiple BRCs to map the magnetic field geometry and strength. On the basis of magnetic field lines orientation in these BRCs we compared our result with the MHD simulations and studied the RDI mode of triggered star formation. More so, we compared these results with the previously studied HII regions, Sh2-131, Sh2-185, Sh2-236 and Sh2-126. Along with magnetic field study, to understand RDI processes, we performed molecular line observations using four lines in two BRCs having different orientations of magnetic field lines with respect to the incoming ionizing radiation. We carried out optical and NIR spectroscopic observations to estimate the mass accretion rates in young stellar objects associated with triggered star forming regions and compared them with non-triggered star-forming regions like Taurus. Furthermore, we made an optical design of Wide-field polarimeter (Wi-Fi Pol) for 1.3m Devasthal Optical telescope and developed a polarimetric data reduction pipeline.


About Speaker: Ms Neha Sharma is research scholar at ARIES and working in the field of Astronomy for her PhD under supervision of Dr Maheswar Gopinathan. This is her thesis Pre-submission talk.



[243] Topic: Fascinating Life-stories of Pulsars

Speaker: Avinash Deshpande
Affiliation: RRI, Bangalore
Date (yyyy-mm-dd): 2016-12-06
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: Pulsars are believed to be strongly magnetized, fast rotating neutron stars, with over 2000 discovered in our Galaxy so far. In the long march towards the elucidation of the mysterious ways of pulsars, a few special ones have taught us more than most of the rest put together. Apart from sharing our understanding of the origin and evolution of these cosmic light-houses,the talk will try to highlight a few illustrious members of the pulsar family, and focus on some of the key messages they bring to us.


About Speaker: Works at Raman Research Institute, Bangalore, in their Astronomy & Astrophysics group, since 1980. An electrical engineer by training(BTech 1980 IIT Kanpur; PhD 1988 IIT Bombay).Primarily engaged in radio astronomy activities.Signal and image processing, instrumentation,and understanding noise & uncertainties are his interests. He has been trying to learn about these issues in the context of pulsars, interstellar medium and radio interferometry.



[242] Topic: Calibration and Validation activities for Earth Observational Satellite

Speaker: Dr. A. K. Mathur
Affiliation: SAC Ahemadabad
Date (yyyy-mm-dd): 2016-11-23
Time: 10:30hr
Venue: ARIES Auditorium

Abstract: The presentation will cover a brief account of calibration and validation activities of various ISRO's Earth Observation satellites sensors and their products. These include Oceansat-1, INSAT-3D/3DR, SARAL, Megha-Tropiques, CARTOSAT and RISAT-1 etc. Also some of the instruments available for calibration and validation at permanent cal-val sites will also be discussed.


About Speaker: Dr A K Mathur is working at SAC, Ahmadabad. He is head of Calibration and Validation Department. He is one of the expert in retrieval of SST and Atmospheric Humidity Profile from Meteorological Satellite.



[241] Topic: Introduction of our recent activities to improve methane emission estimate over South Asia-AMASA Project

Speaker: Prof Sachiko Hayashida
Affiliation: Nara Womens University, Nara
Date (yyyy-mm-dd): 2016-11-17
Time: 11:30hr
Venue: Council Room, Ashiwni Guest House

Abstract: Methane (CH4) is the second most significant anthropogenic greenhouse gas. Most of methane emissions from Asia are attributable to ruminant animals and rice fields, but the quantitative estimate of methane emissions remains highly uncertain.This has led to initiation of a project, called Atmospheric Methane from Agriculture in South Asia (AMASA), to study methane emission estimate from South Asia. This project is supported by Ministry of Environment, Japan. The first goal of the project is to downscale the emission estimate from a global scale into a regional scale and improve methane emission estimate from South Asia by using GOSAT and ground-based data. To accomplish this goal, we are now collaborating with many local scientists and farmers to carry out in-situ measurements in India and Bangladesh. The second goal is to develop some emission mitigation proposals. In this project, we are focusing on methane emission from rice fields. One approach to reduce methane emission from rice fields is an intermittent draining of water, and another approach is a proper fertilizer management. Based on local experimental works on those measures, we will arrange some mitigation scenarios, and input them into an atmospheric transport model to examine if it is realizable or detectable.


About Speaker: Prof Sachiko Hayashida is leading scientist at Nara Women University, Nara. Her research interest is mainly on ground based and space-borne observations.



[240] Topic: Air Quality in the "Anthropocene" Era- a Satellite Perspective

Speaker: Dr Pawan K Bhartia
Affiliation: NASA Goddard Space Flight Center
Date (yyyy-mm-dd): 2016-11-04
Time: 15:30hr
Venue: Auditorium

Abstract: Chemistry Nobel Laureate Paul Crutzen has coined the term “anthropocene” to put the modern industrial era in the geological context to highlight the fact that human-induced changes to the earth are in some cases as large as the changes that occurred in geological times. Though the changes in the terra firma and the biosphere are the most visible manifestations of these changes, the quality of our life-sustaining atmosphere is also changing rapidly. Air quality is affected not only by the “bad air” that we can smell or feel in our lungs but also by the change in the composition of the “good air” that has made life on this planet possible. The most well known of these changes has been the rapid thinning of the ozone layer in the polar regions, popularly known as the Ozone Hole. Satellite images of this phenomenon captured the attention of the world in the mid 80s leading to rapid phase-out of the offending chemicals. Examples of bad air are gases and particulate matter near the surface. I will discuss how modern satellite instruments are tracking them to help the policy makers in tracking appropriate actions.


About Speaker: Dr. Pawan Kumar Bhartia is a Senior Research Scientist at NASA Goddard Space Flight Center, Greenbelt, Maryland, USA. He is an internationally known expert on ultraviolet remote sensing of Earth from space. He led the TOMS Project from 1991 to 2005, which received the William T. Pecora award in 2006, for creating unique long-term datasets from TOMS. He led the Aura/OMI US science team from 2004 to 2011 and currently leads the team that is producing stratospheric ozone and aerosol profiles from the OMPS-limb instrument on the Suomi NPP satellite. He served as the Head of the Atmospheric Chemistry Branch at NASA GSFC from 1994 to 2006. He was elected to the International Ozone Commission in 2008. He is the recipient of William Nordberg medal and Robert H. Goddard Award of Merit from NASA GSFC, Outstanding Leadership and the Distinguished Service Medals from NASA, and the Remote Sensing Prize from the American Meteorological Society. He received Ph. D. in Physics and M.S. in Computer Science from Purdue University, Lafayette, Indiana, and B.Sc (Hon) and M. Sc from Patna University, Patna, India.



[239] Topic: Multi-band Studies of Blazars with XMM-Newton

Speaker: Nibedita Kalita
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-09-30
Time: 15:30hr
Venue: Auditorium

Abstract: Blazars are sub-class of the radio-loud Active Galactic Nuclei (AGN), which emits highly luminous, polarized and non-thermal radiation covering the entire electromagnetic spectrum from a highly compact center (i.e., SMBH). The blazars with higher luminosity and jet angle are known as FSRQs (Flat spectrum radio quasars), while the BL Lac objects show comparatively low luminosity and smaller jet angle (in both cases the jet angle is < 10 degree). Moreover, the SED synchrotron peak of FSRQs lies in the radio to optical range but for BL Lacs the synchrotron hump peaks in UV/X-rays. One of the most interesting phenomenon that blazars show is the multi-frequency flux variation on diverse timescales. The aim of this thesis is to explore the twisted emission mechanisms involved in the local environment of the SMBH that resides at the center of blazars and to study variability properties in multi-wavelength scenario. We have undertaken two different approach to understand the blazar emission; (1) temporal study in multi-frequency domain and (2) X-ray spectral study. The work presented in this thesis is based on the observations made by XMM-Newton observatory. As part of the first approach, we have studied variability on Intraday & Long (years) timescales and correlated variability between optical, UV & X-ray bands for the FSRQ 3C 273 and found that two electron populations with different Lorentz factors are involved in low and high energy emissions. A hardness ratio analysis in the X-ray regime indicates that the particle acceleration mechanism dominates the cooling mechanism during most of the time. An extensive study with possible correlations, variability timescales and QPOs in a sample of ISP blazars in their outburst state, with the most efficient techniques like SF, ACF, DCF & PSD to understand the complex emission from the relativistic jet and the jet structure has also carried out. We have studied the relation between synchrotron peak of multi-band SED and the X-ray IDV for a sample of a dozen of blazars (includes 10 LSPs and 2 ISPs). Here we have concluded that the highest energy electron available for syncrotron emission will have retarded effect on X-ray IDV. X-ray spectral study of the border line blazar 3C 273 in the energy range 2.5-10 keV, from 2000 through 2015 revealed some new information about the source. A new minimum flux state of 3C 273, even lower than the historical minimum during 2003-2004, was observed in 2015. A harder-when-brighter trend is observed in these long-term multi-epoch observations of 3C 273 for the first time. With simultaneous study of the X-ray continuum and ultraviolet emissions during the quiescent state of the source, we have detect a significant anti-correlation between the X-ray spectral slope and the X-ray to UV flux ratio. From this detection we conclude that the 2.5-10 keV X-ray emission is the result of IC scattering of soft UV seed photons in a thermal corona based above the accretion disc.


About Speaker: Nibedita Kalita is a 5th year PhD student working with Dr Alok Gupta. This is her Pre PhD submission talk.



[237] Topic: Kelvin-Helmholtz instability in rotating magnetized solar atmospheric jets

Speaker: Prof Ivan Zhelyazkov
Affiliation: Kelvin-Helmholtz instability in rotating magnetized solar atmospheric jets Ivan
Date (yyyy-mm-dd): 2016-09-22
Time: 15:30hr
Venue: Auditorium

Abstract: We study the conditions under which spinning twisted solar jets observed by Solar Dynamic Observatory (SDO) can become unstable against the Kelvin-Helmholtz (KH) instability. The KH instability arises at the interface of two fluid layers that move with different speeds. Flows are generally uniform in the two layers, however, a strong velocity shear arises near the interface region of these two fluids forming a vortex sheet that become unstable to the spirale-like perturbations. When a magnetic flux tube moves along its axis, a vortex sheet is evolved near tube's boundary which may become unstable against to the KH instability provided that its axial velocity exceeds some critical value. This vortex sheet causes the conversion of the directed flow energy into a turbulent energy.


About Speaker: Prof. Ivan Zhelyazkov is a senior Professor at Faculty of Physics, Sofia University and PI of the Indo—Bulgarian project from Bulgarian side. He is working in the Kelvin-Helmholtz in the solar atmosphere. He has published several research papers in the international journal of repute. He is visiting for here under the Indo-Bulgarian exchange program.



[236] Topic: X-RAY INTRADAY VARIABILITY OF FIVE TEV BLAZARS WITH NUSTAR

Speaker: Ashwani Pandey
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-09-20
Time: 15:30hr
Venue: Auditorium

Abstract: We have examined 40 NuSTAR light curves (LCs) of five TeV emitting high synchrotron peakedblazars: 1ES 0229+200, Mrk 421, Mrk 501, 1ES 1959+650 and PKS 2155−304. Four of the blazars showed intraday variability in the NuSTAR energy range of 3–79 keV. Using a structure function analysis we searched for intraday variability timescales in these LCs and found indications of several between 2.6 and 34.4 ks in five LCs of Mrk 421, and a timescale around 7.5 ks for one LC of Mrk 501. We also employed an auto correlation function analysis and found indications of very similar timescales during those six observations as well as hints of timescales in four additional observations of Mrk 421. The other three blazars’ LCs do not show any evidence for intraday variability timescales shorter than the lengths of those observations; however, the data was both sparser, and noisier, for them. The 22 LCs of Mrk 421 observed between July 2012 and April 2013 show that this source was in a quiescent state for an extended period of time and then underwent an unprecedented double peaked outburst while monitored on a daily basis during 10 – 16 April 2013. We briefly discuss models capable of explaining these blazar emissions.


About Speaker: SRF



[235] Topic: The galaxy life cycle: from activity to quiescence across cosmic times.

Speaker: Abhishek Paswan
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-08-24
Time: 15:30hr
Venue: Auditorium

Abstract: The aim of the discussion is to explain the evolution of galaxies from the blue cloud via the green valley to the red sequence throughout their lives. It is well established that the regulation in star formation in galaxies is the main key which derives galaxies from the blue cloud to the red sequence. In this respect, there are many mechanisms such as AGN feedback, strangulation process and other gas removal processes including ram pressure gas stripping and galaxy-galaxy interaction/merger, which regulate the star formation in galaxies and derive them towards the red sequence. The discussion will shed light on these mechanisms and their roles to explain the galaxy evolution.


About Speaker: SRF



[234] Topic: X-Ray Emission of Supernovae

Speaker: Anjasha Gangopadhyay
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-08-23
Time: 15:30hr
Venue: Auditorium

Abstract: Core collapse supernovae, due to interaction of the shock wave with the circumstellar medium, show emission in the X-ray wavelengths. X-ray emission occurs in supernova due to a prompt thermal burst, compton scattered gamma rays synthesised by the radioactive nucleids or due to the interaction of the shock with the circumstellar medium. X-Ray emission occurs during two phases : one early and one late (> 100 days) in the evolution of supernova. SN 1978K is one of the X-ray rich supernova with long lasting X-ray emission in the recent times. We present the X-ray spectral analysis of SN 1978K. The spectrum is best fit with a "dual vnei" model having variable elemental abundances. Our analysis shows the presence of two temperature plasma - one with a higher temperature and other with a lower temperature . We will briefly describe Chevalier-Fransson model and justify our results with this.


About Speaker: SRF



[233] Topic: DYNAMIC EVOLUTION OF SUPERNOVA REMNANTS

Speaker: Raya Dastidar
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-08-22
Time: 15:30hr
Venue: Auditorium

Abstract: Supernovae are cosmic explosions that mark the end of massive stars and inject a significant amount of energy to the ISM. After the initial shock breakout, the ejecta sweeps through the ISM and finally merges with the ISM. This may last for more than 100000 years. This dynamic evolution of the supernova remnants can be divided into different phases according to the physical processes that dominate during the evolution. I will discuss these phases in detail and show that by applying some reasonable assumptions the typical time scales, expansion velocities and sizes characterizing these phases can be approximately extracted.


About Speaker: SRF



[232] Topic: Accuracy of Upper Tropospheric Humidity Measurements and Present Balloon Measurements in Nainital, India

Speaker: Prof Thomas Peter
Affiliation: Institute for Atmospheric and Climate Science, ETH, Zurich
Date (yyyy-mm-dd): 2016-08-19
Time: 15:30hr
Venue: Auditorium

Abstract: Owing its role as “gateway” to the global stratosphere, knowledge of the tropical tropopause layer with respect to its water budget is important in order to understand the radiative and chemical properties not only of this layer itself, but of the entire stratosphere, including its impact on global climate. Previous measurements suggest that these measurements are very difficult, and no accepted instrumental “gold standard” exists. In particular, instrumental uncertainties have prevented to properly judge to which degree observed persistent extremely high saturation ratios over ice (RHice >> 1.5) within cirrus clouds are real or only an instrumental artifact. Here we show that humidity measurements within cirrus clouds allow to estimate the measurement uncertainty of each instrument, owing to the restoring force that the ice surfaces have on the H2O in the gas phase. The measurements of most instruments can be explained as superposition of this restoring force and small-scale temperature fluctuations, allowing to explain even data points with extreme super‐ or subsaturation. In general, this demonstrates progress in measurement technology applicable to the adverse conditions of the tropical tropopause layer. On the other hand, this analysis makes clear that future improvements in our quantitative understanding of the freeze‐drying process will only be possible if the remaining measurement uncertainties of RHice of ca. 20% can be overcome. Finally, I will confront this analysis with some results from the ballooning activities presently ongoing here in Nainital.


About Speaker: Thomas Peter has been Full Professor for Atmospheric Chemistry at the Institute for Atmospheric and Climate Science since January 1999. Before this, he was leader of the group for heterogeneous chemistry and microphysics of atmospheric aerosols at Max Planck Institute for Chemistry in Mainz. Presently, he is visiting ARIES, Nainital.



[231] Topic: Study of Aerosol Distribution and associated Meteorology over the central Himalayas

Speaker: Raman Solanki
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-08-12
Time: 15:30hr
Venue: Auditorium

Abstract: Air pollution is intrinsically linked with meteorological parameters and this linkage further strengthens over complex mountainous terrain, an attempt to understand this association over a mountain ridge in the central Himalayas through measurements of aerosol vertical distribution, surface layer characteristics and local boundary layer (LBL) evolution is being made. This study presents ground based measurements taken at ARIES, Nainital (Manora Peak, 79.5oE, 29.4oN and 1958 m AMSL) over a period of October 2011 to February 2014. Intermittent LiDAR observations were made during March 2012 to May 2013 out of which 57 suitable cases have been subjected to analysis. A comparison of ground based LiDAR observations with the CALIPSO satellite derived aerosol backscatter profiles has been carried out for 37 suitable cases. The mean percent bias for different seasons are found to be +18±42%, +22±28%, +32±36% and +18±51% for MAMJ-2012, SON-2012, DJF-2012-13 and MAM-2013 respectively. Surface layer characteristics have been studied during spring (2013) and winter (2013-14) season, utilizing the 3-D wind components and virtual temperature observed with sonic anemometers (sampling at 25 Hz) mounted at 12-m and 27-m height on a meteorological tower. A new criterion of SNR > 6 dB for the LBL characterization has been implemented; the resulting estimations are found to be in agreement with radiosonde measurements over the site. The daytime average observed LBL height ranges from 440±197 m in November (late autumn) to 766±317 m in March (early spring). The observations revealed a pronounced impact of mountain-topography on the LBL dynamics during March, when strong winds (> 5.6 m s-1) lead to LBL height of 650 m during nighttime. The RWP measurements of LBL are further utilized to evaluate biases in model simulated boundary layer and the implications of these biases in context with trace species model simulations.


About Speaker: Raman Solanki is pursuing his PhD from ARIES Under the supervision of Dr Narendra Singh, and he is registered with University of Delhi.( It is a pre-submission Seminar)



[230] Topic: Detection of variable stars in M31 galaxy

Speaker: Mr. Rishikesh Gokhale
Affiliation: Mumbai University
Date (yyyy-mm-dd): 2016-08-04
Time: 11:00hr
Venue: Auditorium

Abstract: This project is aimed at finding Cepheids and short as well as long period variable stars in M31 galaxy by studying their photometric characteristics. The data for the present study was obtained from 1.04m Telescope at Manora Peak, Nainital. In this project, initially stars were categorised as pulsating or non-pulsating and their corresponding period is found out by plotting a Periodogram of Power density Vs Frequency using Lomb-Scargle method. Stars with period between 2-100 days were studied for characteristic matching of Cepheids. For this, Period-Luminosity plots for possible Cepheid candidates are made. Then those candidates are plotted on Colour-Magnitude Diagram (CMD) to check whether they lie within Cepheid instability strip within the photometric uncertaintyIn the present analysis, I found one population I Cepheid and one population II Cepheid along with 11 long period and 3 short period variable stars.


About Speaker: Mr Rishikesh Gokhale has done summer project sponsored by Indian Academy of Science.



[229] Topic: Study of ozone and precursors over the Himalayan region

Speaker: Mr Piyush Bhardwaj
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-08-04
Time: 15:30hr
Venue: Auditorium

Abstract: Ozone and related trace gases (CO, NOx, VOCs, etc.) play essential roles in determining air quality, oxidizing capacity of the atmosphere, budgets of various other trace gases and also climate change. The emissions of these gases are increasing over Indian subcontinent owing to rapid growth in economy and higher energy needs. Further, satellite retrievals also indicate high levels of pollution across Indo-Gangetic plain and this pollution under favorable meteorological conditions can be transported to other regions as well, including the pristine Himalayas. In light of above facts, an extensive study performed during a PhD thesis was aimed to understand some of the underlying processes and to fill the gaps through surface based observations of ozone and related trace gases over the Himalayan region during SusKat field campaign and balloon borne observations of ozone and met parameters over Manora Peak, Nainital. During the SusKat observations, it was realized that the discrepancies between the model and observation results could be mainly due coarse resolution of input emission inventories. Additionally, further tuning in the model setup, including testing of various land surface models etc are needed. The use of a chemical box model could also provide in-depth information on the underlying atmospheric chemistry of the region. Here, I propose to setup and use the box-models, improvement in WRF-Chem setup over the Himalayan region, improvement in emission inventories. Some campaign based specific vertical measurements of ozone and meteorological parameters could be carried-out during my PDF tenure at ARIES to investigate above mentioned objectives.


About Speaker: Mr Piyush Bhardwaj has applied for the PDF position at ARIES.



[228] Topic: Studies of Ring Galaxy

Speaker: Dr. Alka Mishra
Affiliation: ARIES, Manora Peak, Nainital
Date (yyyy-mm-dd): 2016-08-02
Time: 15:30hr
Venue: Auditorium

Abstract: Ring galaxies are very interesting objects. Their most prominent feature is the lack of a typical spiral structure, replaced by a narrow, ring-shaped accumulation of gas and stars. Such a peculiar distribution of matter is believed to form during collision of a spiral, gas-rich small galaxy with a early-type one . For small impact collision generates a ring-shaped structure in the disk in which the stellar and gaseous material crowd together. Large impact collision produce crescent-shaped rings with an off-centred remnant nucleus. In both cases the ring contains many massive, relatively young blue stars, which are extremely bright. The central region contains relatively little luminous matter.


About Speaker: Working as a PDF at ARIES



[227] Topic: Atmospheric bioaerosols in the Earth System: Climate and ecosystem interaction in Indian perspective

Speaker: Dr Sachin Gunthe
Affiliation: IIT Madras ( Chennai)
Date (yyyy-mm-dd): 2016-07-28
Time: 15:30hr
Venue: Auditorium

Abstract: Atmospheric aerosols of biological origin are ubiquitous in the Earth’s atmosphere and play an important role in Erath’s climate and ecosystem health. These bioaerosols mainly include airborne bacteria, fungal spores, pollens, plant and animal fragments, etc. These bioaerosols are essential for reproduction and spread of organisms across various ecosystems by means of air dispersal. During dispersal, however, they can cause or enhance human, plant, and animal diseases. Moreover, they can also serve as nuclei for cloud droplets and ice crystal thus affecting the hydrological cycle. The abundance, diversity, and implications of bioserosols on climate and ecosystem health, however, is not well characterized and leaves a wide gap in the scientific understanding of their interactions with climate and ecosystem. Over the Indian region, which has a diverse land-use pattern and experiences the contrasting synoptic scale weather phenomenon by means of Southwest and Northeast monsoon, the characteristic source properties of bioaerosols and their impact on climate and human health exhibit manifold implications. I will present the novel bioaerosol measurements carried out over Indian region at contrasting locations during distinct seasons using advanced state-of-the-art techniques.


About Speaker: Dr Gunthe is Assistant Professor and Head Max Planck Partner Group at IIT Madras, Department of civil Engineering,IIT Madras.



[226] Topic: X-ray super-flares on CC Eri

Speaker: Subhajeet Karmakar
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-07-21
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: We present an in-depth study of two superflares detected on active binary system CC Eridani by Swift observatory. The first flare (F1) triggered the Burst Alert Telescope (BAT) in the hard X-ray band on 2008 October 16, whereas the second flare (F2) triggered BAT on 2012 February 24. The rise phases of both the flares were observed only with BAT, whereas the decay phase was observed simultaneously with X-Ray Telescope (XRT) and BAT. The e-folding decay time indicates a faster decay in hard X-ray band than in soft X-ray. The peak X-ray luminosity for flares F1 and F2 in the 0.3–50.0 keV energy band (excluding 10–14 keV band) reached up to 3×1032 and 5×10^31 erg s^−1, which is ∼3500 and ∼600 times more than the quiescent value, respectively and larger than any other previous flares observed on CC Eri. Spectral analysis indicates a presence of three temperature corona with first two plasma temperatures remain constant during the flares at ∼3 and ∼10 MK. The flare-temperature peaked at 342 MK and 119 MK for F1 and F2, which are ∼4 and ∼2 times more than the mini- mum value. The abundances peaked at 2.0 and 1.2 solar abundances, which is larger than a factor ∼11 and ∼7 than quiescent state value. Using hydrodynamic loop modeling we derive loop-lengths for both flares as 1.25±0.13×10^10 cm and 1.26±0.20×10^10 cm, respectively. The Fe Kα emission at 6.4 keV was also detected in the X-ray spectra, and we model the Kα emission feature as fluorescence from the hot flare source irradiating the photospheric iron. Our analysis indicates the flare location is in any one of the binary components withan astrocentric angle of ∼85–90◦ .


About Speaker: SRF at ARIES



[225] Topic: Role of "Radiation Driven Implosion" in Star Formation Process

Speaker: Piyali Saha
Affiliation: JRF
Date (yyyy-mm-dd): 2016-07-19
Time: 15:30hr
Venue: Auditorium

Abstract: Interstellar HII regions are formed through joint effects of the wind and ionizing radiation produced by one or more early type stars. In the early phase of HII region, a rapid R-type ionization front propagates out to the Stromgren radius. This ionisation front typically drives a shock into the initial cloud. The clouds will be compressed by the ionisation-shock front and eventually star formation takes place. This process is termed as 'Radiation Driven Implosion' and is considered to be responsible for sequential star formation. The way how the ionisation-shock front propagates into an initially spherical cloud and how star formation takes place in the RDI mode will be explained in the talk.


About Speaker: JRF at ARIES



[224] Topic: Study of CO2 and other trace gases using CRDS technique

Speaker: Krishna Anil Kedia
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-07-13
Time: 15:30hr
Venue: Auditorium

Abstract: Cavity Ring Down Spectroscopy (CRDS) technique has a wide range of applications in atmospheric sciences as this single instrument is capable of measuring different gases with very high accuracy and sensitivity. Observations of CO2, CO and CH4 are being made at Nainital using CRDS. The diurnal pattern of these trace gases is mainly influenced by upslope and downslope mountain winds which is an important phenomena in high altitude sites. The boundary layer processes and role of OH chemistry is also playing an important role.


About Speaker: Mr. Krishna is from IISER, Bhopal and pursuing BS-MS dual degree (2nd year). He is doing a project under SRFP of Academies.



[223] Topic: Effect of mountain induced atmospheric waves on the trace chemical species over Himalayan region

Speaker: Sweta Kumari
Affiliation: Indian School of Mines, Dhanbad
Date (yyyy-mm-dd): 2016-07-12
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: This report presents first and preliminary results on the ozone depletion due to mountain induced atmospheric waves. Analysis of plots from Microwave Limb Sounder(MLS) instrument onboard Aura (NASA's satellite) affirms our hypothesis that mountain waves play a crucial role in Himalayan region atmospheric chemistry.


About Speaker: Ms Sweta Kumari is Btech Environmental Engineering fourth year student at Indian School of Mines, Dhanbad and is doing a summer research fellows, Indian Academy of sciences in ARIES from May-July 2016



[221] Topic: Photometric Study Of CW leonis(IRC +10216 )

Speaker: Sankalp Mishra
Affiliation: Indian Institute Of Science Education And Research, Thiruvananthapuram
Date (yyyy-mm-dd): 2016-07-05
Time: 11:00hr
Venue: Auditorium

Abstract: I will be presenting my work on Photometric Study Of CW Leonis. This talk includes the correction of raw images for the error induced by the CCD and Aperture photometry is for target star (CW Leonis) and 5 comparison star (randomly selected) to find their flux for many apertures by using IRAF. By usual procedure, best aperture is selected and two comparison stars of similar brightness are chosen by examining the light curves.Light curves (differential magnitude Vs time) are successfully generated for target stars,for best two apertures and time period is calculated.


About Speaker: I am currently pursuing Integrated MS majoring in Physic and minor in Mathematics at IISER TVM.



[220] Topic: Photometric study of open cluster NGC1893

Speaker: Abinaya Swaruba
Affiliation: Christ College, Bangalore
Date (yyyy-mm-dd): 2016-06-30
Time: 11:30hr
Venue: Auditorium

Abstract: I will be presenting my work on photometric study of open cluster NGC1893


About Speaker: Summer Fellow, Indian Academy of Science



[219] Topic: Time series CCD photometry of exoplanet corot 24b

Speaker: Aarushi Gupta
Affiliation: Amity University, Noida
Date (yyyy-mm-dd): 2016-06-30
Time: 11:00hr
Venue: Auditorium

Abstract: My talk is about detection and analysis of a transit in the light curves of the exoplanet corot 24b. I have done data reduction, aperture photometry and differential photometry for my analysis using IRAF.


About Speaker: Ms Aarushi Gupta is a Bsc physics honors second year student at Amity University, Noida and is doing a summer internship in ARIES from May-June 2016



[218] Topic: Development of On-chip Photonic Instruments for Astronomical Spectroscopy

Speaker: Pradip Gatkine
Affiliation: University of Maryland at College Park, USA
Date (yyyy-mm-dd): 2016-07-07
Time: 15:30hr
Venue: Auditorium

Abstract: The next-generation of ground-based extremely large telescopes (ELTs) in optical and NIR will have diameters in the range of thirty meters (such as TMT). The volume, mass, and cost of the instrument scale roughly as diameter cubed. This necessitates the development of suitable seeing limited spectroscopic instrumentation. Astrophotonics is the next-generation approach that provides the means to miniaturize near-infrared (NIR) spectrometers for upcoming large telescopes and make them more robust and inexpensive. Arrayed waveguide gratings (AWG) is one such technology suitable for astronomical spectroscopy. We have developed on-chip AWG spectrographs in H-band of near-infrared suitable for astronomical applications. We have also simulated Fiber Bragg Grating (FBG) based OH-emission suppression in NIR (H band and J band) for observing high redshift (6-12) GRB afterglows. I will summarize our recent work on these astrophotonic technologies (AWG and Bragg Gratings) and their broad implications to astronomy. Astrophotonics has a potential to be a paradigm-shifting development for future ground-, balloon- and space-based telescopes.


About Speaker: Astronomy graduate student at University of Maryland at College Park, USA



[217] Topic: Intriguing aspects of Atmospheric Waves over the Himalayan region as revealed by ground based and satellite observations

Speaker: Dr K Niranjan Kumar
Affiliation: University of Tokyo
Date (yyyy-mm-dd): 2016-06-30
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: In this talk, my focus will be mainly on the atmospheric waves and mesoscale dynamics with special emphasis on surrounding deep convection, Himalayan Mountains, and the jet streams. The properties of atmospheric waves, their sources and their many effects in the atmosphere are studied using the various observational techniques includes Satellite remote sensing (AIRS, CALIPSO, MLS), balloon-borne radiosonde observations along with global model reanalysis data sets such as ECMWF, NCEP/NCAR, MERRA etc. The three-dimensional properties of atmospheric gravity waves are important in estimating momentum flux. Also, the parameterization schemes used in the global circulation models (GCMs) are still based on simplifying assumptions and estimates of momentum flux is still rely on models than on measurements. To estimate the gravity wave momentum flux it is required to obtain the simultaneous measurement of horizontal and vertical. Hence, in order to achieve this, we have used some innovative techniques using the advanced space-borne measurements such as Atmospheric Infrared Sounder (AIRS), to image the gravity waves in three dimensions and hence estimated the momentum flux over the Himalayan Mountains. Further, my recent focus is on the dynamics of heavy rainfall events over the central Himalayan region and will share some preliminary and interesting observations for which the detailed analysis is still under progress. In this context, I will also like to discuss about the predictability of extreme weather over the Uttarakhand and adjoining mountainous regions through the response of the upper tropospheric Rossby waves and synoptic-scale circulations.


About Speaker: Dr Niranjan Kumar is expert in lower and upper atmospheric wave dynamics with special emphasis on the extreme rainfall events over local, regional and global scales.



[216] Topic: A temporal and spectral study of GRB afterglows

Speaker: Atharva Rawte
Affiliation: D. G. Ruparel College Mumbai
Date (yyyy-mm-dd): 2016-06-28
Time: 11:00hr
Venue: Auditorium

Abstract: In this project, I have studied the Swift XRT light curves of long duration GRBs. The X-ray light curves show a variety of properties - some decaying with a single powerlaw and some showing a break in the light curves. Based on the estimated jet-break time, we estimate the energetics and opening angle of the GRBs.


About Speaker: Mr. Atharva Rawte is B. Sc. Second year student at D. G. Ruparel College, Mumbai and is pursuing the academy summer fellowship in ARIES from May-June 2016.



[215] Topic: Studies of Nearby Star Forming Galaxies

Speaker: Sumit Jaiswal
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-06-30
Time: 15:30hr
Venue: Aries Auditorium

Abstract: Star formation plays a major role in galaxy evolution and its energetics over cosmic time. We have selected a sample of 26 Wolf-Rayet (WR) galaxies to study the star formation scenario in galaxies. The galaxy-galaxy tidal interaction is expected to be fundamental mechanism which triggers star formation in galaxies. We have performed HI 21-cm line and H-alpha line imaging of these galaxies to see the interaction features in the selected galaxies. The H-alpha observations together with archival data from various surveys provide very important correlations between star formation rates estimated using different radiation mechanisms. The radio-FIR correlation in WR galaxies is also estimated.


About Speaker: Ph.D. Student



[214] Topic: Boundary layer evolution over the central Himalayas from Radio Wind Profiler and Model Simulations

Speaker: Dr Narendra Singh
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-06-24
Time: 15:30hr
Venue: Auditorium

Abstract: Investigation on the Time-evolution of Local Boundary Layer (LBL)is carried out over a mountain ridge at Nainital (79.5oE, 29.4oN, 1958 m amsl) in the central Himalayan region, using a Radar Wind Profiler (RWP) during November 2011 to March 2012, as a part of the Ganges Valley Aerosol Experiment (GVAX). The study is restricted to clear-sunny days, resulting in a total of 78 days of observations. The standard criterion of the peak in the signal-to-noise ratio (SNR) profile was found to be inadequate in the characterization of Mixed Layer (ML) top at this site. Therefore, we implemented a new criterion of SNR > = 6 dB for the characterization of the ML and the resulting estimations are shown to be in agreement with radiosonde measurements over this site. The daytime average (0500-1000 UTC) observed boundary layer height ranges from 440±197 m in November (late autumn) to 766±317 m above ground level (AGL) in March (early spring). The observations revealed a pronounced impact of mountain-topography on the LBL dynamics during March, when strong winds (> 5.6 m s-1) lead to LBL heights of 650 m during nighttime.These results are also utilized to evaluate WRM model for boundary layer.Sensitivity simulations using a Mixed Layer model (MXL/MESSy) were also carried out which indicated that the springtime overestimation of LBL would lead to a minor uncertainty in simulated surface ozone concentrations.


About Speaker: Narendra Singh is working as a Scientist in the Atmospheric Science Group.



[213] Topic: High resolution simulation of CO2 transport by a regional model WRF-CO2 over South Asian region

Speaker: Srabanti Ballav
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-06-17
Time: 14:30hr
Venue: Auditorium

Abstract: The increase of atmospheric CO2 concentration due to anthropogenic activities and hence induced climate change has captured the attention and concern of human society. In this regard, the high resolution forward transport model simulations of CO2 at hourly to synoptic timescales have attracted considerable interest in recent time. This becomes important for predicting the future climate to a high degree of certainty. Extensive studies using high resolution CO2 forward transport models are carried out over the United State, Europe and East Asia. However, such studies are very few over South Asia. In view of this, a high resolution regional forward transport model, Weather Research Forecast model for CO2 (WRF-CO2) is being setup for South Asia to better understand the spatial and temporal CO2 variations over this region. Here, a fully coupled, online, regional air quality model WRF-CO2 has been setup and used for the first time to simulate long term CO2 over South Asian region. Comparison of the model results with the ground–based measurements indicates that the model reproduces the spatial and temporal variation of CO2 concentration with higher bias during the growing season. Model results from WRF-CO2 are able to resolve fine scale structures and are facilitating interpretation of CO2 observations. The WRF-CO2 model was able to reproduce the diurnal pattern of CO2 concentration for two observation stations but amplitude of diurnal cycle of CO2 is not captured by the model, particularly over growing season.


About Speaker: She is a Post-Doctoral Fellow at ARIES and this is her first year review talk.



[212] Topic: On the nature of radio-quiet weak emission line quasars.

Speaker: Parveen Kumar
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-06-17
Time: 15:45hr
Venue: Auditorium

Abstract: The Sloan Digital Sky Survey (SDSS) and Two-Degree Field QSO Redshift Survey (2QZ) have revealed a population of Active Galactic Nuclei (AGNs) with peculiar spectral characteristics. These objects have featureless optical discovery spectra resembling BL Lac objects. However, they are significantly quiet in radio and X-ray bands compared to classical BL Lacs. These objects could therefore belong to the hitherto unrecognised population of radio-quiet BL Lacs or radio- quiet quasars without a Broad Line Region (BLR). How such objects fit into the AGN unification picture is an open question. Polarization and variability are the two main characteristic properties of BL Lac objects. Last year, I was involved in two such project, first one is polarisation and spectroscopy study of radio-quiet BL Lacs. For this we carried out spectral and polarisation measurements of a sample of 19 such RQWLQs. Out of them only 9 sources show non-significant proper motion, and all of them show percentage polarisation (P) less than 1%, except two sources J142505.59+035336.2 and J154515.77+003235.2 with highest polarization 1.59 ± 0.53%. This small percentage polarisation of RQWLQs seems too low for them to be the radio-quite analogue of Bl-lac objects. We also report a statistical comparative study of the spectral slope, temporal variation of the continuum flux at different time scales using a sample of 45 RQWLQs with 900 redshift-luminosity matched control sample of QSOs and 120 blazar collected from the literature. The structure function analysis shows that the mechanism triggering the optical variability in RQWLQs seems similar to that in QSOs and unlike blazar which are generally highly variable at all time scales. Similarly, the spectral slop distribution of RQWLQs differ at high significance from that of blazars, suggesting that the mechanism of RQWLQs central engine might be resembling more with that of normal QSOs, perhaps with less developed BLR as a cause of their weak emission lines; unlike the Bl-lac/blazar objects whose continuum emission are dominated mainly by their relativistic jet. The paper has been written and submission is expected in next two three weeks.


About Speaker: Mr. Parveen Kumar is a 4th year student working with Dr. Hum Chand



[211] Topic: Study of cool gas outflows from AGNs

Speaker: Ms. Sapna Mishra
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-06-16
Time: 14:30hr
Venue: Auditorium

Abstract: This year I have focused on cool outflows associated with class of AGN known as Blazars. It is believed that the cool gas clouds (eg.MgII absorption system) with velocities βc ≤ 5000 km/s relative to the background quasars are associated to quasar itself (associated system) however absorber with velocity offset beyond this limit are ‘intervening system’ and their presence is completely independent of background quasar. Recent evidence, however, appears to question this canonical view and suggests that even associated systems can have significantly relativistic velocities relative to the background quasar, in case the quasar is undergoing powerful jet activity and/or ejecting high speed accretion-disk outflows (Bergeron et al.2011). A possible signature of this would be if the occurrence rate, dN/dz, of ‘intervening’ absorbers is found to differ for background sources with and without powerful jets. The reason behind this departure is attributed to the powerful jets activities along the line of sight of observer which are responsible for an excess in value of dN/dz and hence are the main source of intrinsic cool outflows. With this motivation whether or not the existence of excess cool absorbers is related to background source we have used a sample of 97 Blazars with 0.5


About Speaker: Ms. Sapna is a 2nd year student working with Dr. Hum Chand.



[210] Topic: On the INOV Properties of X-ray Bright NLSy1 Galaxies and Photometric Reverberation Mapping of AGN.

Speaker: Mr. Vineet Ojha
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-06-16
Time: 15:45hr
Venue: Auditorium

Abstract: Broadly my research work would be based on the “Multi-wavelength study of Active galactic Nuclei(AGN)”. This year I have mainly focused on a class of AGN called Narrow line Seyfert 1 (NLSy1) galaxy. The sample consist of well selected 18 NLSy1 galaxies, which are at least detected in X-ray at more than 3σ level. The aim to choose X-ray bright NLSy1 is to explore the origin of X-ray emission since generally Seyfert galaxies are less prominent in high energy band. The other motivation was the recent surprising discovery of gamma-ray emission from dozen of NLSy1 galaxies, which has been associated to the presence of jets in their center, generally found in elliptical radio galaxies/rather than in spiral galaxies. So one possibility is that may be the cause of X-ray emission in X-ray detected NLSy1 galaxies might also be associated to the mild jet activity in their center, as proposed gamma-ray detected NLSy1 galaxies. Higher duty cycle of Intra-night optical variability is one of the diagnostic commonly used to quantify significant jet activity where even small fluctuation in flux can get Doppler boosted. Therefore we have used the ARIES 1.3m DFOT telescope for the INOV study of our sample. As of now about 16 sources have been monitored each lasting for more than 3.5 hours. The data has been analyzed and paper is almost in final stage. Out of the total 16 session we have not found any source which show variability after applying robust statistical tests. This suggests the absence of jet dominance as for as X-ray emission is concerned, though our source being faint the improvement required higher sensitivity using 2m class telescopes. Our group is also involved in making the catalog of NLSy1 galaxy based on large data-set of 1.5 million AGN from SDSS-DR12, which I plan to use to prepare a sub-sample for their multi-wavelength study especially with ARIES 3.6m DOT for optical and astro-sat for X-rays for detail study in my thesis. In addition, I was also a part of photometric reverberation campaign carried on 15 night from 1.3m telescope. My involvement was assisting the observation and then reduction of the data in two broad and one narrow band, which has been also completed. This program is to characterize the L-R relation of broad line region of low luminosity AGN.


About Speaker: Mr. Vineet is a 2nd year student working with Dr. Hum Chand.



[209] Topic: Assessment of carbonaceous aerosols over northern part of India: Mass level and its impact on regional climate

Speaker: Dr Suresh Tiwari
Affiliation: Indian Institute of Tropical Meteorology, New Delhi Branch
Date (yyyy-mm-dd): 2016-06-22
Time: 15:30hr
Venue: Auditorium

Abstract: Carbonaceous aerosols, (organic carbon: OC and black carbon/elemental carbon: BC/EC) constitute a significant fraction (∼10–70%) of the fine mode particles (PM2.5: particle cut-off diameters d ≤ 2.5 μm) have gain significant importance in aerosol research due to adverse effects on human health, environmental issues as visibility impairment, regional air pollution, etc. and are emitted into the atmosphere together by open biomass burning, indoor biomass/biofuel combustion for cooking and heating, and fossil fuels combustion. OC, is a cooling agent (a scattering particle), is emitted both as primary aerosols and as volatile organic gases that are subsequently converted to the secondary organic aerosols, however, BC, a climate-warming agent (an absorbing particle) is mostly emitted into the atmosphere from primary sources. Indo-Gangetic plains (IGP) which is one of the highly populated and polluted region in the world due to a higher loading of atmospheric aerosols produced by both natural as well as anthropogenic sources, is located in the northern part of India. Recent studies indicated that the level of PM2.5 over IGP region is greater than 120 µgm-3 (annual mean) which is 3 and 10 times higher than the Indian National Ambient air Quality standard and US-EPA standard respectively. The contribution of carbonaceous aerosols to fine mode particles are ~ 40%. Due to the higher mass concentrations of BC, the mean atmospheric heating rates were observed greater than 2 K day−1 over this region and it would probably galvanize in the strengthening of temperature inversion which further leads to the poor dispersion and affecting the formation of clouds. We have taken several in-situ observations over IGP region of carbonaceous aerosols and found tremendous high concentrations. In details, we will discuss in my presentation. Our study suggests that the serious detrimental impacts on regional climate due to the high concentrations of carbonaceous aerosols and are suggested that the competent authority will take immediate and stringent measures to improve the regional air quality in the northern part of India.


About Speaker: Dr S Tiwari is at Indian Institute of Tropical Meteorology, New Delhi Branch. He is the scientist incharge of the branch. His research interest is on rain water precipitation, aerosol optical, physical and chemical properties and its radiative impact.



[208] Topic: Bright Rimmed Cloud: A Potential Site of Triggered Star Formation

Speaker: Piyali Saha
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-06-15
Time: 14:30hr
Venue: Auditorium

Abstract: Bright Rimmed clouds (BRCs) are small molecular clouds located at the periphery of evolved HII regions with their 'bright rims' facing towards ionising star(s) side. They are believed to be the potential sites of triggered star formation due to the pressure exerted by the incoming ionising radiation from the massive ionising star(s). Thus, they are good examples of the radiation driven implosion (RDI) mode of triggered star formation. But, star formation frequency, star formation efficiency and stellar mass function due to RDI are still unknown. Details of RDI mode can be acquired by observing a number of BRCs that are classified as triggered and non-triggered based on previous studies. For this purpose, pilot study has been done on two BRCs, namely SFO 18 and SFO 38 which are considered as non-triggered and triggered respectively. We have mapped thsese BRCs with 12CO, C18O, N2H+ and HCN (J=1- 0 transition) lines to understand the dynamics, excitation temperature, column density and optical depth traced by these lines. By using continuum emissions in far-infrared region we have estimated dust temperature, spectral emissivity index and other physical parameters of the dust present in these two BRCs. Priliminary results will be discussed in my talk.


About Speaker: Ms. Piyali Saha is a 2nd year student working with Dr. Maheswar G.



[207] Topic: Optical Study of Core Collapse Supernovae and their progenitor environment.

Speaker: Raya Dastidar
Affiliation: Aries
Date (yyyy-mm-dd): 2016-06-15
Time: 15:45hr
Venue: Auditorium

Abstract: Observed properties of core-collapse supernovae (ccSNe), such as light curve and spectra are governed by the properties and environment of the progenitor star. Stripped envelope supernovae, a subclass of ccSNe, takes under its wings type Ib, Ic and IIb SNe. As the name aptly suggests, the progenitor star is stripped of its envelope prior to explosion. The extent of stripping depends on the environment of the star and/or the presence of a massive binary companion. We present in this report the broad band BVRI investigations of SN 2012P in the galaxy NGC 5806 obtained during 2012 Jan 24 to Jun 27. A photometric follow up was initiated within 2 days after the discovery (Jan 22), but due to the late discovery of the event the peak was not covered. We used χ2 minimization technique to determine the explosion epoch by fitting the SN 1993J light curve to our light curve. This suggested a probable explosion epoch which is 16 days prior to its discovery. Hence, we adopted 2012 Jan 6 as the possible explosion epoch. Further, we eliminated the host galaxy contamination underlying the SN position using High Order Transform of Psf And Template Subtraction software with template images acquired on 2013 April 14, almost a year later. It is found that the light curve of SN 2012P obtained from the difference images closely resembles SN 1993J, a prototype of this subclass, during the first∼50 days, but the event SN 2012P is considerably fainter than other well studied type IIb events.


About Speaker: Ms. Raya Dastidar is a 2nd year student working with Dr.Brijesh Kumar



[206] Topic: REVIEW REPORT (Second year) Broad-band photometric survey of zenith sky at Nainital

Speaker: Pankaj
Affiliation: Aries
Date (yyyy-mm-dd): 2016-06-14
Time: 15:45hr
Venue: Auditorium

Abstract: We present the scheme and preliminary results of a broadband photometric survey of zenith sky at latitude (29.4 deg) of Nainital. The aim of the survey is to generate fainter standard stars in the 30 arcmin strip of the zenith sky. This data can be used for a wide vari- ety of astronomical topics as well as technical characterization of telescope and instruments. This limited zenith sky survey is being done at broad-band U,B,V,R and I lters using 1kХ1k CCD mounted with the 104-cm telescope, the work involves observation-calibration of the photometric images.


About Speaker: Mr. Pankaj is a 2nd year student working with Dr. Brijesh Kumar



[205] Topic: Optical Studies Of Stripped Envelope Supernova

Speaker: Anjasha Gangopadhyay
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-06-13
Time: 14:30hr
Venue: Auditorium

Abstract: Context We present the optical studies (ugriz, BVRI) of a type IIb supernova SN2015as. Super- novae(SNe) IIb show a variety both in light curve and spectral features. An analysis of this has been done. Data has been taken from 104-cm Sampurnanand Telescope, 130-cm Dev- asthal Fast Optical Telescope (DFOT), 200-cm Himalayan Chandra Telescope and 182-cm Asiago Ekar Telescope. Four epochs of UV data has also been taken with Swift UVOT. Aim We study the optical light curve evolution of a Type IIb supernova (SN) 2015as starting from 1 to 150 day after discovery and the spectral evolution of this SN at two epochs. We also present the apparent, absolute magnitude light curve and colour curve of SN2015as. Method Raw data(Optical) taken from different telescopes was first preprocessed using IRAF soft- ware. Basic photometric reductions has been done using the DAOPHOT package. Results and Discussion Although the peak of the BVRI lightcurve could not be covered since the first observation was taken after 17days from discovery, but the ugriz evolution was studied from 2 days after discovery. We fit a spline function to r and i bands to estimate peak magnitude and time. The r and i band light curves peaked around 22 and 27 days respectively after explosion with a peak magnitude of 14.26 and 14.96 respectively. The extinction corrected (V-I) and (R-I) light curves show that the SN 2015as is much bluer than other SN of this group. Also, the absolute magnitude curve for the V band shows that the absolute magnitude is much less as compared to other members of this group and peaks around -17 mag. From the spectral evolution, we see that the +19 day spectrum of SN2015as showed broad P-cygni absorption of Hα (λ6563Å) and absorption due to Hβ, Hγ and Ca II H and K. The spectra around 19 days also shows He features at λ5876Å. This marks the property of type IIb SN that shows transition from initial H to He features. Also, in late time spectra red region shows OI and Mg II lines.


About Speaker: Ms. Anjasha Gangopadhyay is a 2nd year student working with Dr. Kuntal Mishra



[204] Topic: Spatial and Temporal indices of Indian Monsoon Rainfall

Speaker: Dr M S Narayanan
Affiliation: S R M University
Date (yyyy-mm-dd): 2016-06-09
Time: 15:30hr
Venue: Auditorium

Abstract: Indian summer monsoon rainfall (ISMR) has three important attributes for its proper representation – viz total seasonal quantum, its spatial and temporal distribution over the different Indian land mass for the four monsoonal months. Traditionally only the all India area – weighted average rainfall of the season as a whole, has been used as a single index to study the interannual variations and teleconnections with other global parameters. In this study, using 115 years of ISMR gridded data, we have proposed two new indices - the Temporal and the Spatial Indices, besides the Quantum Index (in vogue). These indices for any year depend on the number of Normal rainfall Days and number of Normal rainfall Grids during the year. It is suggested that the incorporating all three indices will be a better way to study the Indian monsoon intra seasonal – inter annual variabilities. Case studies of a few good and poor monsoon years are discussed to highlight the importance of the new indices.


About Speaker: Dr M S Narayanan is at SRM University. He was group director SAC,ISRO,Ahmedabad. His research interest is on satellite remote sensing, with focus on monsoon rainfall.



[203] Topic: Rainfall estimation from Satellites - how far are they from reality ?

Speaker: Dr M S Narayanan
Affiliation: S R M University
Date (yyyy-mm-dd): 2016-06-08
Time: 15:30hr
Venue: Auditorium

Abstract: The recent heavy rainfall events over Chennai on Nov 15 – 16 and on Nov 30 – Dec 1, 2015 have provided an excellent opportunity to inter compare the rainfall estimates from satellites - GPM, INSAT – 3D; Chennai Doppler Radar and ground raingauges. The results show wide disparity between the various estimates, posing the basic question as to the spatio temporal scales at which any one could be a substitute for the other. Our studies to inter compare TRMM merged rainfall products with IMD gridded rainfall over Indian land mass from 15 years of concurrent data, have shown that on daily scale, only beyond 5 x 5 deg spatial average, the two satellite estimates and ground measurements have semblance of compatibility. Details of this study which has been performed for different rain rates will be presented.


About Speaker: Dr M S Narayanan is at SRM University. He was group director SAC,ISRO,Ahmedabad. His research interest is on satellite remote sensing, with focus on monsoon rainfall.



[202] Topic: Flare, Surge Eruption and the evolution of Photospheric Doppler enhancements

Speaker: Aabha Monga
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-06-07
Time: 14:30hr
Venue: Auditorium

Abstract: In this review, I am going to present the multi-wavelength analysis of C6.1/SF are occurred on June 12, 2010 from active region NOAA AR 1081 with the complexity of βγ and was associated with Type II radio burst and Coronal Mass Ejection (CME). We have used ARIES Hα data, SDO- AIA/HMI, SoHO-LASCO and STEREO/SECHHI data for this study. The are is accompanied by surge like ejection and later produce Type II radio burst with a slow CME( 382 Kms/sec) and initially CME speed was high ( 700 Kms/sec). Here we report the co-spatial evolution of the Doppler enhancements and the chromospheric Hα ribbons observed during X1.2 Class are observed on May 15, 2013. The velocity enhancements exactly match the Hα brightness enhancements with the delay of approximate 2 minutes delay.


About Speaker: Mrs. Aabha Monga is a 4th year student working with Dr. Wahab Uddin.



[201] Topic: Multi-Wavelength study of Magnetic CVs

Speaker: Arti Joshi
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-06-07
Time: 15:45hr
Venue: Auditorium

Abstract: We present analyses of archival X-ray data obtained from the XMM-Newton satellite of an intermediate polar V2400 Oph. The X-ray variations occur at the 1003-s synodic period which is strongly indicated in the power spectrum of the time series. The blackbody temperature of irradiated poles of the white dwarf atmosphere is found to be 90 eV, much higher than those found in their synchronous analogues, the Polars. The EPIC-PN spectra shows the presence of soft X-ray components. Blackbody-like emission, similar to that seen in soft IPs - however through higher absorption, probably arises from the white dwarf surface. The temperature of the optically thin postshock plasma is well constrained 13 keV, being strongly absorbed by dense material with an equivalent hydrogen column density of 8.2×1022 cm -2, which partially cover 36±2 % of the Xray source together with Fe Kα emission line. The new observations support V2400 Oph to be a discless accreting system. We also present the phase-resolved spectroscopy in 0.1-10.0 keV energy range and found that spectral parameters are phase dependent. Photometric and Polarimetric observations of eighteen unidentified magnetic CVs were also carried out in 130 nights from 1-m class telescopes of ARIES, Nainital. Among all these CVs we also present optical results of the four candidates IPHASJ013+622, IPHASJ025+635, IPHASJ034+533 and IPHASJ051+294. Three of the systems IPHASJ013+622, IPHASJ025+635 and IPHASJ051+294 were found to be eclipsing from photometric data. Orbital periods of these CVs lie above the period gap of 2-3 h, which indicates that these can be classified as an intermediate polars.


About Speaker: Ms. Arti Joshi is a 4th year student working with Dr. J. C. Pandey.



[200] Topic: Investigating the Behaviour of Exploding Stars

Speaker: Mridweeka Singh
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-06-06
Time: 14:30hr
Venue: Auditorium

Abstract: Supernovae are the dominant sources of stellar feedback, which plays an important role in regulating galaxy formation and evolution. During the previous five observing seasons from October 2014 to April 2016 we observed a number of events covering various subtypes of SNe such as Ia, Ia-pec, Ib and IIP starting from nearly 10 days after discovery and lasting upto approximately 200 days. Amongst these we present photometric and spectroscopic evolution of a type Ia-pec event SN 2014dt in M61. We present the light curve studies, evolution of colors and compare the luminosity of SN 2014dt with other peculiar events of Ia class. The spectra of SN 2014dt at 22d and 67d after explosion is compared with SN 2005hk at similar epochs.


About Speaker: Ms. Mridweeka Singh is a 3rd year student working with Dr. Kuntal Mishra.



[198] Topic: Probing physical properties of dark molecular cloud L1157

Speaker: Ekta Sharma
Affiliation: Aries
Date (yyyy-mm-dd): 2016-06-14
Time: 14:30hr
Venue: Auditorium

Abstract: In order to understand the whole process of star formation, it is important to have a comprehensive understanding of the evolution of dense cores. The low mass star-forming regions are ideal labo- ratories for such studies because low mass young stars evolve much more slowly and the sample of low mass stars is also relatively large as compared to high mass stars. Therefore, the complete knowledge about different physical properties of the cloud can be extracted out using different observations. Here, the L1157 dark molecular cloud has been studied. The work is being reported into two parts: 1) Magnetic field studies in the dark cloud using optical polarimetry and 2) Molec- ular line studies using radio observations of CO, C18 O, N2H+, HCN molecules. The plane-of-the sky component of the magnetic field is obtained from polarization maps and different parameters from these spectral lines data is calculated. This will help in charaterising about the different evolutionary stages of the cloud that will eventually give rise to star formation.


About Speaker: Mrs.Ekta sharma is a 2nd year student working with Dr. Maheswar G



[196] Topic: Cosmic Microwave Background as a Probe of Cosmic Magnetic Fields

Speaker: T. R. Seshadri
Affiliation: Delhi University
Date (yyyy-mm-dd): 2016-06-06
Time: 15:45hr
Venue: Auditorium

Abstract: We still do not have a fully satisfactory theory of the origin of cosmic magnetic fields. Placing constraints of these fields could play an important role in deciding which of the models are likely to be the plausible ones. The polarization and power spectrum of CMBR could be an important probe in this endeavor. The focus of the talk will be to show how the polarization, power spectrum, bispectrum and trispectrum could place constraints on the strength of these fields.


About Speaker: Professor T. R. Sesahdri is a faculty in the Department of Physics and Astrophysics, University of Delhi, Delhi. He works on Cosmology.



[195] Topic: Study of Galactic Star Forming Regions and related Instrumentation

Speaker: Ms. Neha Sharma
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-06-10
Time: 15:45hr
Venue: Auditorium

Abstract: My thesis is divided into two parts: Part-I The main theme of this part is a) To study the characteristic properties of triggered star formation due to cloud-cloud collision and radiation driven implosion processes using optical polarimetry and molecular lines (12CO, C18O, HCN and N2H+) observations. b) To study the accretion properties of young stellar objects associated with the bright-rimmed clouds using near-IR spectroscopy. c) To study the dust and gas properties of λ-Ori HII using multi-wavelength optical polarimetry, Planck and WISE archival data. Part-II The main theme of this part is to develop a) A complete Zemax design of a wide field optical polarimeter to be used with 1.3m telescope - WiFi-Pol. b) A pipeline software in python that can be used to reduce polarimetric data of AIMPOL and WiFi-Pol.


About Speaker: Ms. Neha is a 5th year student working with Dr. Maheswar G.



[194] Topic: Spectro-Photometric Study of Star Forming Galaxies

Speaker: Abhishek Paswan
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-06-10
Time: 14:30hr
Venue: Auditorium

Abstract: In this thesis, our aim is to understand and constrain star formation in different types of galax- ies. For our study, we have chosen two samples – (i) A sample of late-type galaxies having recent and active star formation. (ii) A sample of early-type galaxies which are normally believed to be quiescent galaxies. Both the samples are selected from SDSS (Sloan Digital Sky Survey). We present here – (1) Data analysis of 20 late-type galaxies with their star formation rate (SFR) and Hα mor- phology using 1.3-m Devasthal telescope. (2) A detailed study of nuclei of Mrk 22 (Blue compact dwarf galaxy) in spectroscopy using 2-m HCT. (3) Constraining very low-level SFR in a sample of early-type galaxies using 1.4-GHz radio continuum data from VLA.


About Speaker: Mr. Abhishek is a 5th year student working with Dr. Amitesh Omar



[193] Topic: General Relativistic Study of Radiatively Driven Jets and Presence of Internal Shocks

Speaker: Mukesh Kumar Vyas
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-06-06
Time: 11:30hr
Venue: Auditorium

Abstract: We study a relativistic fluid jet driven by radiation from accretion disc around a non-rotating black hole. We compute the radiative moments with full relativistic transformations including the effect of bending of light in presence of gravity. We show that the jets, under specific cross section deviates from spherical flow, and exhibits multiple sonic points and internal shocks. We obtain multiple shocks and studied their stability properties.


About Speaker: Mr. Mukesh Kr. Vyas is a 3rd year student working with Dr. Indranil.



[192] Topic: MHD Outflows and Accretion Model with Fixed and Variable Gamma Equation of State

Speaker: Kuldeep Singh
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-06-06
Time: 10:30hr
Venue: Auditorium

Abstract: We study MHD outflows with variable adiabatic index. We then find proper boundary conditions for accretion flow and WD model of magnetic field. For correct boundary conditions, we found accretion solutions for fixed and variable gamma using MHD equations.


About Speaker: Mr. Kuldeep is a 2nd year student working with Dr. Indranil.



[191] Topic: Multi-wavelength Studies of Blazars

Speaker: Ashwani Pandey
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-06-13
Time: 15:45hr
Venue: Auditorium

Abstract: We present here the work done by us in last one year and also our future plans. We are working on two projects : radio to optical cross-correlation study of the blazar PKS 2155-304 and the x-ray intra-day variability of blazars with Nuclear Spectroscopic Telescope Array (NuSTAR). In the optical part of our first project we generated ~ 12 years optical R-band light curve of the blazar PKS 2155-304. By using the structure function (SF) and the auto- correlation function (ACF), we found eight possible periods which indicate two possibilities: an optical periodicity of ~ 311 days and multiple periods with their harmonics. We also generated more than three dozen light curves of blazars using NuSTAR data. We performed SF analysis and also estimated excess variance for these light curves.


About Speaker: Mr. Ashwani Pandey is a 2nd year student working with Dr. Alok C. Gupta.



[190] Topic: Study of magnetic activities on late-type stars

Speaker: Subhajeet Karmakar
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-06-01
Time: 15:30hr
Venue: Auditorium

Abstract: The solar-type stars show rich variety of magnetic activities such as surface inhomogeneities due to presence of dark spots, short and long-term variations in spot-cycles and flares. Using Swift observations, we present an in-depth study of two superflares (F1 and F2) detected on active binary system CC Eridani. The peak X-ray luminosity in 0.3-50.0 keV reached up to 3×10^32 erg/s and 5×10^31 erg/s, which is ∼3500 and ∼600 times more than the quiescent value and larger than any other previously observed flares on CC Eri. Spectral analysis indicates a presence of three temperature corona with first two plasma temperatures remain constant during the flares at ∼3 MK and ∼10 MK. The flare-temperature peaked at 342 MK and 119 MK for F1 and F2, which is ∼4 and ∼2 times more than the minimum value. The abundances peaked at 2.0 and 1.2 solar abundances, which is larger than a factor 11 and 7 than quiescent values. Using hydrodynamic modeling we derive loop-lengths for both flares to be 1.25±0.13×10^10 cm and 1.26±0.20×10^10 cm, respectively. Significant amount of heating is detected during the decay of both the flares. We model the K-alpha emission feature as fluorescence from the hot flare source irradiating the photospheric iron, and estimate the location of the flare at an astrocentic angle of ∼88.2◦. Using the Kepler observations we have analysed an F-type ultra-fast rotator KIC 6791060. We have developed an automated flare search algorithm to detect the flare and to automatically identify the flare start and end time. During the observations, a total of 38 optical flares are detected. Energies of these flares have been found to vary within a range of 1031−34 erg. Preliminary results of surface temperature modeling indicate an existence of two active longitude region on the stellar surface.


About Speaker: Mr Subhajeet Karmakar is a 5th year PhD student working with Dr. Jeewan C Pandey.



[189] Topic: Study of the Tropospheric trace gases over the Indian subcontinent

Speaker: Piyush Bhardwaj
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-06-01
Time: 14:30hr
Venue: Auditorium

Abstract: The Indian subcontinent is among the most populated and highly polluted regions in the world and emissions are increasing over this region due to rapid economic growth here. These increasing emissions have strong implications not only for the large population residing in this region but it can also reach other parts of the world via long range transport. This region is among the least studied parts of the world and limited observations hampers the better understanding of the changing atmospheric chemistry over the region. This thesis describes results from two field campaigns viz., SusKat and GVAX over the Himalayan region; satellite based study of biomass burning over the Indian subcontinent, and balloon borne measurements of ozone and meteorological parameters over ARIES, Manora Peak. The seasonal and interannual distribution of biomass burning activity (2003-2013) indicated distinct seasonal cycle over this region and show that the fire activity has increased during last five years (2008-2013). Large differences were observed in the budgets of trace species emitted during these fires. The emissions show biannual peaks in spring (Mar-May) and autumn (Sep-Nov) season with higher emissions in the later season. For the first time, a field campaign for the measurement of trace species was conducted in Kathmandu Valley, Nepal during Jan-Jun 2013. The ozone and CO levels at Bode, Nepal in the valley were found to be higher than Pantnagar, India. The regional scale pollution from IGP is suggested to contribute to the higher levels during an event in spring season. For the first time high resolution WRF-Chem model setup was done over the Himalayan region and model is able to capture variations in temperature, RH and winds. Model also showed good agreement in daytime levels of CO however, ozone and NOx were over and underestimated. The long term change in the vertical distribution of ozone was studied using balloon borne measurements at ARIES, Manora Peak. The contribution of spring time biomass burning to the ozone levels in lower troposphere is also estimated. Results obtained using the high frequency balloon-borne measurements of meteorological parameters during Ganga Valley Aerosols experiment (GVAX) at ARIES, Nainital indicated high wind speed (~85 m/s) near the subtropical jet. The observations also showed better agreement of wind speeds at 250 hPa (altitude of subtropical jet) than other levels with reanalysis datasets The Satellite based retrievals indicated negative bias in temperature profiles in the lower altitude region, and positive bias near the tropopause. WRF simulated results are able to capture variations in temperature, humidity and wind speed profile reasonable well. The detailed results will be discussed during the talk.


About Speaker: Mr Piyush Bhardwaj is a Research Scholar in atmospheric science group and pursuing PhD with Manish Naja. This is a presentation related with his pre PhD thesis submission.



[187] Topic: Probing the Universe and fundamental physics with QSOs absorption lines

Speaker: Prof. R. Srianand
Affiliation: IUCAA
Date (yyyy-mm-dd): 2016-05-25
Time: 15:30hr
Venue: ARIES auditorium

Abstract: Absorption lines seen in the spectra of high-z QSOs allow one to probe the cosmology, galaxy formation and its evolution. In particular the detectability of absorption does not depend on the luminosity of the absorbing source, it provides a luminosity unbiased tracer of the universe. In addition to probing cosmological evolution one will be able to place stringent constraints on the variations of fundamental constants. In this talk the author will review the present status of the field and summarize future programmes with TMT.


About Speaker: Prof. Srianand, senior professor at IUCAA, is involved in various observational and theoretical projects: 1) probing the physical conditions in the high-z proto-galaxies traced by DLAs, 2) probing the time and space variation of fundamental constants using very high resolution spectra of QSOs, 3) tracing the redshift evolution of the CMB temperature using fine-structure lines and 4) semi-analytic modelling of formation and evolution of IGM, reionization and redshift evolution of global star formation rate density in the universe.



[186] Topic: QSOs absorption line(QSOABL)- tool to probe the evolution of Universe

Speaker: Sapna Mishra
Affiliation: ARIES NAINITAL
Date (yyyy-mm-dd): 2016-05-24
Time: 15:30hr
Venue: Auditorium

Abstract: Study of absorption line systems seen in the spectra of distant QSOs, has played a remarkable role in probing the evolution of the Universe. Tremendous amount of research has been done on absorption line systems e.g. Lyman-alpha forest, Lyman-limit and Damped Lyman alpha systems along the line of sight of QSOs which is a unique tool to prob the proto-galaxy at high redshift. Their studies are important in predicting the physical and kinematic properties of intervening galaxies and IGM. With this idea I will discuss the major research and conclusions made in the field of astronomy from the studies of QSOABL. At the end I will relate my research work with the study of the absorption system of these high redshift objects


About Speaker: JRF at ARIES



[185] Topic: A step toward realization of a large Optical-NIR telescope in India

Speaker: DR PADMAKAR S PARIHAR
Affiliation: IIA Bangalore
Date (yyyy-mm-dd): 2016-05-20
Time: 15:30hr
Venue: Auditorium

Abstract: Recently install 3.6m Devasthal Optical Telescope (DOT) and forthcoming Thirty Meter Telescope(TMT) would not be enough to cater the need of growing Indian astronomical community. Access to 10-12m size optical-NIR telescope equipped with state of the art back-end instruments can bridge the gap between DOT and TMT. A telescope of this size is only possible when primary mirror is made of smaller mirror segments. In order to get acquainted with segmented mirror telescope technology, in IIA we have initiated a project to develop a small prototype telescope made of seven spherical mirror segments (PSMT). I will present the progress made in opto-mechanical design as well development of other sub-systems required for the PSMT. The prototyping effort is one step toward realization of a large telescope in India and it is expected to be completed in 2 years period.


About Speaker: Dr. Padmakar is a Associate Professor at IIA, Bangalore and involved in astronomical instrumentation.



[184] Topic: Constraining Cosmological Baryonic Density Using Primordial Nucleosynthesis

Speaker: Anurag Mishra
Affiliation: IIST, Trivandrum
Date (yyyy-mm-dd): 2016-05-18
Time: 15:30hr
Venue: ARIES auditorium

Abstract: Cosmological Microwave Background (CMB) observations in past 50 years have provided wealth of information about Cosmological Parameters. Planck CMB observations favour Universe dominated by Dark Energy (69%) and amount of Baryonic matter is about 2%. It turns out that using Primordial abundances of light nuclei some of the Cosmological Parameters can be constrained. Deuterium, that undergoes very less astration, is the best ‘Baryometer’ and is used to constrain cosmological Baryonic Density Parameter. In this talk we will focus on how Primodial Nucleosynthesis can be used as a tool to constrain Baryonic parameter using Quasar absorption line studies. In this context our recent result based on analysis to measure Deuterium abundance, along QSO J1558-0031 observed with HIRES/Keck, will also be presented.


About Speaker: Anurag Mishra has just completed B.Tech. (Physical Sciences) at IIST, Trivandrum through ISAT program.



[182] Topic: India s MOM [Mars Orbiter Mission]

Speaker: Dr. S M Ahmed
Affiliation: University of Hyderabad
Date (yyyy-mm-dd): 2016-05-17
Time: 15:30hr
Venue: Auditorium

Abstract: The human quest to learn more beyond earth has taken them to moon in the mid-70s; presently there is rush to catch up with the closest planet – MARS, in un raveling secrets of any trace of life on our nearest neighbor. The Indian space craft, Mars Orbiter Mission, MOM reached Mars after travelling a grueling distance of around 60-crore kms from Earth. While reaching the Mars itself had been very tricky with many failed attempts on part of NASA, erstwhile USSR, ESA; with a success rate of around 36% to-date, India became the FIRST country ever, to reach Mars in its first attempt. In the capacity of core science team member of Chandrayaan-I project, the author had first-hand experience in developing an indigenous science payload, CHACE a quadrupole mass spectrometer, as a part of Moon Impact Probe (MIP) mission. The discussion would revolve around the unique features of planet Mars, the challenges faced by the space craft in reaching to its target, quest for measuring the trace gas methane and details of a set 5-instrumntes it carries.


About Speaker: Dr. S. M. Ahmed is heading the Central Instruments Laboratory as Principal Scientific Officer at the University of Hyderabad. Dr. Ahmed obtained his Ph.D. from the Physical Research Laboratory, Ahmedabad. He has worked at IPR, JPL, EPFL, and VSSC. He joined ISRO s most ambitious Chandrayaan project in 2004 and developed a quadrupole based mass spectrometer, CHACE, which worked successfully in the Moon Impact Probe mission.



[181] Topic: Multi-wavelength analysis of short-duration GRBs using 10.4m GTC and other telescopes during 2012-2015

Speaker: Shashi Bhushan Pandey
Affiliation: Sc-D
Date (yyyy-mm-dd): 2016-05-12
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: {We aim to investigate the prompt emission and afterglow properties of short-duration GRBs including GRB 130603B and other events observed during 2012-2015.} {Multi-wavelength prompt emission and afterglow data of total eight short duration gamma-ray bursts were calibrated to study the temporal and spectral properties.} {Earliest ground-based optical photometry, millimeter-wavelength observations and spectroscopy of GRB 130603B and multi-band data of other seven short duration bursts were used to constrain the nature of these energetic explosions.} {For GRB 130603B, the new data including the earliest photometric observations and the published ones broadly follow the ISM afterglow model. Modeling of the host galaxy of this burst using LePHARE model supports that the environment of this burst is undergoing with moderate star formation activity. Our observations support the requirement for rather early and deeper multi-band observations of many of these events to detect the afterglow or to constrain the possible blue emission from associated ``kilonovae'.}


About Speaker: The speaker is at ARIES and work towards energetic transient events. This presentation is to submit a paper to A&A based on the data discussed in the paper.



[180] Topic: Astrophysical shocks in Hydrodynamic and Magnetohydrodynamic regime

Speaker: Kuldeep Singh
Affiliation: ARIES NAINITAL
Date (yyyy-mm-dd): 2016-05-10
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: The starting of the talk comprises the perturbation in the fluid flow and their analysis under linear assumption. Then I will discuss how these perturbations lead to the formation of shocks. Then we will discuss the theoretical aspects of Hydrodynamic and Magnetohydrodynamic shocks in detail. The latter part will consist of their implications in astrophysical context.


About Speaker: JRF



[179] Topic: HI Emission from Low surface Brightness Galaxies

Speaker: Alka Mishra
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-05-06
Time: 15:30hr
Venue: Auditorium

Abstract: We present HI observations of four giant low surface brightness (GLSB) galaxies UGC 1378, UGC 1922, UGC 4422 and UM 163 using the Giant Meterwave Radio Telescope (GMRT) as part of the study of seven GLSB galaxies in HI and radio continuum (Mishra et al. 2015). LSB galaxies are late type spirals, either blue or red in color, with diffuse stellar disk and wide range in morphology. We examine the morphology and the dynamics. HI is detected from all the galaxies and the extent is roughly twice the optical size and found the HI masses of the order of ≥ 109 M⊙. We combine our results with those in literature to further understand these systems. Recent star formation traced by near-ultraviolet emission in the GLSB galaxies in our sample appears to be located in rings around the galaxy centre.


About Speaker: She is a PDF at ARIES and she has applied for the extension.



[178] Topic: Application of VHF radars for monitoring atmospheric structure and dynamics: Gap areas

Speaker: Dr M Venkat Ratnam
Affiliation: National Atmospheric Research Laboratory
Date (yyyy-mm-dd): 2016-05-05
Time: 11:30hr
Venue: ARIES Auditorium

Abstract: VHF radars have evolved as powerful tool for monitoring Earths atmosphere. It has several advantageous over other techniques as they provide observations with high temporal and vertical resolutions. Most advantage is providing 3-D wind fields particularly the vertical wind which made it unique among other techniques. These radars are effectively utilized for basic atmospheric research besides its operational applications (forecasting, aviation, wind support for rocket launches and air quality meteorology). Fundamental research includes boundary layer processes, turbulence, wave dynamics, stability of the atmosphere, retrieval of temperature and humidity, tropical tropopause layer characteristics, stratosphere -troposphere exchange processes, Indian summer monsoon dynamics (low level jet, tropical easterly jet, monsoon circulation), Hadley circulation, mesospheric and ionospheric dynamics, lower, middle and upper atmosphere coupling processes. Present talk summarizes all these applications. It also covers identification of few gap areas while using network of such radars (existing and upcoming) and adding complementary techniques.


About Speaker: Dr M Venkat Ratnam is Scientist-F in Atmospheric structure and Dynamics Group, National Atmospheric Research Laboratory, Gadanki, ISRO, Department of Space. He is an expert in Lower and Upper Atmospheric Dynamics. He has been actively involved in several national and international campaigns (CAWSES etc).



[175] Topic: Ambipolar Diffusion

Speaker: Ekta Sharma
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-04-12
Time: 15:30hr
Venue: Auditorium

Abstract: Stars are inevitable offsprings of self-gravity of interstellar matter once it becomes comparable to the disruptive forces due to magnetic fields, thermal pressure. In magnetic mediated theory of star formation, the gravitational collpase of clouds is believed to take place through “ambipolar diffusion”. I will discuss the role of Ambipolar Diffusion in star formation and how it can explain the possible time scale of dynamical collapse.


About Speaker: She is a second year PhD student and working with Dr Maheswar Gopinathan.



[174] Topic: General relativistic description of accretion-ejection mechanism around black holes

Speaker: Rajiv Kumar
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-04-05
Time: 15:30hr
Venue: Auditorium

Abstract: We want to understand the black hole accretion process, outflows and jets, and predict its observational properties. In the study of accretion disc the highly non-linear process involves a transport of angular momentum by turbulent viscosity process and dissipation in the disc by various dissipative process. The disc in a full general relativistic regime is a very hard to study analytically. So here firstly, we have study analytically hydrodynamic disc with using pseudo-Newtonian potential (pNp) around black holes then using full general relativistic (GR) approach. We have compared our analytical accretion solutions with simulation results around black holes. We have developed all type of possible accretion solutions in the disc with using pNp as well as GR. We have mainly focused on shock disc solutions and jets solutions by assuming jet geometry around the black hole. We computed the jet streamline above the equatorial plane using von-Zeipel surfaces and also estimated the mass outflow rates from the disc with using GR approach for non-rotating black holes. In future, we want to do this type of study for rotating black holes.


About Speaker: Mr Rajiv is a PDF at ARIES working with Dr Indranil.



[173] Topic: Multi-wavelength Studies of Blazars

Speaker: Ms Aditi Agarwal
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-04-08
Time: 15:30hr
Venue: Auditorium

Abstract: Active Galactic Nuclei (AGNs) are extremely powerful objects emitting over a wide range of wavelengths from radio to gamma-rays. An AGN is a complex system consisting of the central super-massive black hole, an accretion disk, dusty torus, and clouds of gas orbiting the black hole, as well as out-flowing matter (which moves away from the central black hole) in the form of collimated relativistic jets. Two major classes of AGNs that have been established are radio-loud and radio-quiet. Flat spectrum radio quasars (FSRQs) and BL Lacerate objects (BL Lacertae) together are coined as blazars, a subset of core dominated radio-loud AGNs, known to be variable at all accessible time scales over entire EM spectra. The spectral energy distribution (SED) of blazars display two well-defined broad spectral components. Blazars are the special laboratories for extreme physics which we would like to explore. The analysis presented in this thesis is aimed to provide a more detailed multi-wavelength understanding of blazars. We have analyzed Optical and Radio observations together with multi-frequency archival data of blazars in order to study flux-colour variability at diverse timescales, possible quasi-periodic oscillations (QPOs), correlated variability, multi-band SEDs, spectral Indices variations and core shift effect. We have developed statistical techniques and the analysis methodology to extract the maximum possible information from an observed blazar light curve. We have carried out quasi-simultaneous and relatively dense temporal observations of four blazars (2 BL Lacertae and 2 FSRQs) during the observing season 2012 − 2016. This is extensive study of these blazars on all timescales. Also, we searched for the colour variations on intraday and short timescales but significant colour variation was observed only on few instances for these targets which can be attributed to the models involving shock propagating down the jets. We searched for possible correlations between colour and magnitude and obtain that all blazars followed the bluer-when-brighter trend which can be explained by the shock-in-jet models. From the intraday LCs, we inferred the variations to be simultaneous in both the filters which was confirmed by Discrete correlation function (DCF) analysis technique. Optical QPOs were found in blazars on intra-day timescales and can be explained by the fluctuations induced by the disk. Assuming the possible weak QPOs in the blazars are real and are associated with the innermost portions of their accretion disk, we estimated their central black hole masses. We presented first detailed investigation of the core shifts with frequency, along with estimation of jet physical parameters in the case of our source sample, observed using single dish observations at five radio frequency bands. We have calculated and explained the parameters that can be derived from the analysis of the radio light curves, including the magnetic field strength and size of the emitting core, based on physical models proposed in earlier literature.


About Speaker: She is Research Scholar and pursing Ph D under supervision of Dr Alok Gupta. This is her Pre PhD submission talk.



[172] Topic: Hydrodynamics Instabilities in Astrophysical and Atmospheric context

Speaker: Mukesh Kumar Vyas
Affiliation: ARIES, MANORA PEAK, NAINITAL
Date (yyyy-mm-dd): 2016-03-14
Time: 15:45hr
Venue: Auditorium

Abstract: I will sketch the theoretical origin and physical understanding of Rayleigh Taylor and Kelvin Helmholtz instabilities in fluids. This will be followed by their simulations and numerous cases in nature including daily life, earth atmosphere and astrophysical objects (Like Supernovae and crab nebula)


About Speaker: Research Fellow, ARIES



[171] Topic: Multi-wavelength Studies of Active Galactic Nuclei

Speaker: Jai Bhagwan
Affiliation: ARIES, MANORA PEAK, NAINITAL
Date (yyyy-mm-dd): 2016-03-04
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: Active Galactic Nuclei (AGN), refers to the existence of energetic phenomena in the nuclei, or central regions, of galaxies which can not be attributed to stars. AGN has a super-massive black hole at its center which accretes matter. Two major classes of AGNs are radio-quiet and radio-loud AGN. In my Ph.D. thesis, I have worked on a sub-class of radio-loud AGN called blazars. The blazars, I selected for my studies are TeV emitting blazars and known as TeV blazars. Blazars emit radiation in the complete EM spectrum. Their flux and polarization are highly variable on all diverse timescales and emission is predominately nonthermal. My thesis results has 2 parts: (1) Multi-wavelength (optical/UV, and X-ray) observations of the TeV blazar PKS 2155 - 304 with XMM-Newton, (2) Multi-band optical observations of 3 TeV blazars; on diverse timescales. (1) Using ~ 12 years XMM-Newton archival simultaneous data in optical/UV and X-ray bands of PKS 2155 - 304, we studied flux and spectral variability on diverse timescales and have tried to model the spectral energy distribution (SED). In a specific observation, we noticed the evidence of particle acceleration and synchrotron cooling both are at work for the first time. We also estimated the various parameters of SEDs. (2) In multi-band optical studies of 3 TeV blazars, we have made new observations using 5 telescopes (2 in ARIES, 1 in Bulgaria, 1 in Greece, and 1 in Serbia). We have studied flux and color variations in these 3 TeV blazars on diverse timescales as short i.e. few tens of minutes and as long i.e. few years. We discuss the possible physical mechanisms most likely responsible for the observed flux variability.


About Speaker: Mr. Jai Bhagwan joined ARIES as a Ph.D. student in August 2010 and after completing one year of pre-Ph.D. course work he joined his research project in supervision of Dr. Alok C. Gupta. In December 2013, he joined PG Teacher, Physics job in a Government college in Rohtak, Haryana. His Ph.D. work is completed and he will be submitting his Ph.D. thesis in Raipur University on next week.



[170] Topic: Observations of Accreting Binaries, Transients and Targets of Opportunity at SAAO

Speaker: Prof. David Buckley
Affiliation: South African Astronomical Observatory
Date (yyyy-mm-dd): 2016-01-29
Time: 11:30hr
Venue: Auditorium

Abstract: I will discuss observations conducted with SALT and other SAAO telescopes of transients and other targets of opportunity, with an emphasis on accreting binaries, namely cataclysmic variables and X-ray binaries. The recently established MASTER-SAAO optical transient detection facility will be described, plus the recent results following from this, particularly relating to new CV discoveries. Future plans for followup observations of transients, detected by various facilities, with SALT and other facilities will also be presented.


About Speaker: Prof. Buckley has been deeply associated with the SALT, the 10-meter class optical telescope in South Africa.



[169] Topic: Ozone and Atmospheric Transport

Speaker: David W Tarasick
Affiliation: Evironmental and Climate Change Canada
Date (yyyy-mm-dd): 2016-01-29
Time: 15:30hr
Venue: Auditorium

Abstract: Ozone has been studied since the 1930s, in large part because of its properties as a tracer of atmospheric motion. Although recent interest in ozone focuses on its importance as an absorber of UV and IR radiation (and thereby an important greenhouse gas), and as a tropospheric oxidant and pollutant, the relatively long chemical lifetime of ozone in both the stratosphere and the troposphere means that transport is as important as chemistry to understanding the past and present, and predicting the future distribution of ozone in the atmosphere. In Canada routine measurements of the vertical profile of ozone concentration using balloon-borne ozonesondes have been carried at Resolute Bay since 1966, making this record the longest in the world. Ozonesondes are currently flown weekly at eight sites, making the Canadian network also one of the largest in the world, and particularly important for studies of ozone changes over the past half-century. Since its early use in the 1970s, atmospheric Lagrangian transport (trajectory) modeling, driven by increasingly sophisticated and accurate numerical weather prediction models, has become a powerful tool for studying the transport of atmospheric tracers like ozone. Although these data are sparse both in space and time, they have high vertical resolution, and can be extended by trajectory mapping to other locations and times. This is possible because the lifetime of ozone is of the order of weeks in the troposphere, and months or more in the stratosphere. This widely available technique has numerous applications to the study of ozone processes, and has been essential to current understanding of Arctic ozone depletion, and stratosphere-troposphere exchange. Recent uses of trajectory mapping in ozone data assimilation and in ozone source attribution will also be shown. A recent application of trajectory mapping to the entire global ozonesonde dataset has produced a unique three-dimensional global ozone dataset from the late 1960s to the present day. Although developed initially as climatology for use as an a priori for models and for satellite retrievals, the dataset can also be used for the study of regional and global ozone trends, stratosphere-troposphere relationships, and the regional representativeness of individual sounding sites.


About Speaker: Prof. David W. Tarasick (Evironmental and Climate Change Canada, Ontario, Canada) is responsible for Canadian Ozonesonde Network, which is the largest network in world with a site of longest record (since 1966) of observations. He is co-inventor of UV Index (1992). He has chaired different scientific program on ozone and also SSC member of TOAR (Tropospheric Ozone Assessment Report). He is involved in different international campaign e.g. (BORTAS, IONS, ARCTAS, etc).



[168] Topic: Optical Hα imaging and spectroscopy of a Wolf-Rayet galaxy Mrk 22

Speaker: Abhishek Paswan
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-01-25
Time: 11:00hr
Venue: Auditorium

Abstract: We present results from narrow-band Hα imaging and optical spectroscopy on a blue compact dwarf (BCD) Wolf-Rayet (WR) galaxy, Mrk 22. The WR emission features namely the blue and red bumps in the optical spectrum are detected. The detection of this WR features indicates that the origin of ionized gas in galaxy could be attributed to existing young massive stars. Hence, the population of hot massive stars in galaxy is also quantified using the WR bumps luminosity. The star formation rate is estimated as 0.04 ± 0.01 solar mass per year. For this region, age of the most recent starburst is found as 5.8 ± 0.7 Myr old using Hα and Hβ equivalent widths. The GMRT HI 21cm - line radio observation reveals that the most likely triggering mechanism responsible for this starburst is interaction or merger with an HI cloud. Furthermore, the physical condition and chemical abundance for various elements are derived. Subsequently, the Oxygen abundance is also estimated from electron temperature of the ionized gas.


About Speaker: Mr. Abhishek Paswan is a research scholar at ARIES.



[167] Topic: A study on Dynamical aspects of Aerosols over the central Himalayan region

Speaker: Krishna Kumar Shukla
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-12-31
Time: 11:00hr
Venue: Auditorium

Abstract: Atmospheric aerosols are an important entity and are the subject for research in current scenario due to their diverse physical and optical properties. In my thesis work, we have reported the findings on the intriguing aspects of boundary layer and wave induced aerosol dynamics over a high altitude site in central Himalayan region. We have used the Doppler Lidar (DL) and other collocated instruments along with satellite datasets during Ganges valley aerosols experiment (GVAX) 2011-2012 to understand the morphological characteristics of aerosols, long-range trasnport and associated dynamics over the site. Also, we have estimated cloud base height over this site for the first time using Doppler lidar and other collocated instruments and found reasonably good correlation of cloud base heights estimated with different methods and instruments. Now, we would like to extend our work by validating the ground based instruments (Doppler Lidar, Ceilometer etc) with different satellite datasets (space borne Lidar satellite (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO)), MODIS, AIRS, CLOUDSAT) over a complex topographic region in the central Himalayan region. During my doctoral work, we have also attempted to understand the short period and long period modulations which could provide a clue of understanding additional heating rates in the atmosphere in episodic events. Now, we will also take long term datasets of different ground based and also global datasets to understand the affect of planetary scale wave modulations over our region. Apart from this, a ST-Radar facility is also coming up at ARIES which will provide high vertical and temporal resolution tropospheric wind measurements which will be used to understand lower tropospheric dynamics over Central Himalayan region.


About Speaker: Mr. Krishna Kumar Shukla has submitted his Ph D thesis under supervision of Dr. Phani Kumar and has applied for the PDF position at ARIES.



[166] Topic: Global Nanotechnology Research for Healthcare

Speaker: Dr Anil Patri
Affiliation: US FDA
Date (yyyy-mm-dd): 2015-12-28
Time: 15:30hr
Venue: Auditorium

Abstract: New upcoming field of Nanotechnology and its use in healthcare is a leading research topic worldwide. Application of different kinds of nanomaterial in the medicine will be discussed. Details of global funding and coordinated research by US Food and Drug Administration will also be described.


About Speaker: Dr Anil Patri is Director of Nanocore and Chair of the Nanotechnology Task Force at US Food and Drug Administration (FDA). He also serves as the co-chair of US-EU communities of research in Nanotechnology.



[165] Topic: Molecular line diagnostic of the radiation-driven implosion mode of triggered star formation in bright rimmed clouds

Speaker: Neha Sharma
Affiliation: ARIES
Date (yyyy-mm-dd): 2016-01-12
Time: 15:30hr
Venue: Auditorium

Abstract: Bright rimmed clouds (BRCs) are the isolated molecular clouds located at the periphery of relatively evolved HII regions, which are found to have many signs of star formation. We present the preliminary results of the pilot study conducted on the two BRCs, BRC 18 and BRC 38 basically to assess the feasibility of mapping observations with HCN (1-0) and N2H+ (1-0) molecular lines using KVN single dish facility. The main aim of this study was to understand the kinematics of the radiation-driven implosion mode of triggered star formation in BRCs.


About Speaker: Ms Neha Sharma is a 5th year Research Scholar working in the field of Astronomy under the supervision of Dr. Maheswar Gopinathan.



[164] Topic: Demonstration of NI Lab VIEW, My RIO & NI ELVI

Speaker: Abhimanyu Mahajan
Affiliation: Starcom information Technology Ltd
Date (yyyy-mm-dd): 2015-12-18
Time: 09:30hr
Venue: ARIES Audotorium

Abstract: Demonstration of NI Lab VIEW, My RIO & NI ELVI


About Speaker: Senior Product Engineer of Starcom Information Technology Ltd



[163] Topic: Spatial and Temporal enhancements in Eruptive events

Speaker: Aabha Monga
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-12-17
Time: 15:30hr
Venue: Auditorium

Abstract: I have analyzed the region AR12437 where C2.1 class flare occurred in the South-West area of the Sun observed on October 26, 2015. From the morphological studies, flare eruption shows the Three ribbon structure. This region was least complex with the complexity α. Filament was associated with this flare. Besides the circular ribbon, an inner and an outer (remote) ribbons are often found. I have analyze the event with SDO/AIA and HMI data for the evolutionary studies. This study is also characterized with the X-ray emission to study the energy release processes. I have also used ARIES Hα data and velocity Dopplergrams for the Photospheric study of the region AR11748 for the Intensity- velocity relations.


About Speaker: Ms Aabha Monga is a 4th year Research Scholar working in the field of Solar Physics under the supervision of Dr. Wahab Uddin.



[162] Topic: Study of sparse star clusters and metallicity distribution of the Large Magellanic Cloud.

Speaker: Samyaday Choudhury
Affiliation: IIA Bangalore
Date (yyyy-mm-dd): 2015-12-02
Time: 15:30hr
Venue: Auditorium

Abstract: The Magellanic Clouds (MCs), comprising of the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC) are two nearby (~50 kpc), interacting galaxies to our Milky Way. In my thesis, I have studied the sparse star clusters and metallicity distribution for one of the component of the MCs, the LMC. The study of sparse star clusters in the LMC is important in order to understand the cluster formation history of the LMC. The study aims to increase our understanding of sparse star clusters in the LMC, using deep Washington photometric data of 45 star clusters obtained from 4 m Blanco Telescope, CTIO. A systematic study was performed to estimate their parameters (radius, reddening, and age) using the main-sequence turn-off, as well as the evolved portion of the color-magnitude diagram (CMD). The basic parameters were estimated for 33 clusters, out of which 23 are identified as single clusters and 10 are found to be members of double clusters. The other 12 cluster candidates have been classified as possible clusters/asterisms. This study emphasises that the LMC has a significant population of clusters, which are similar to the open clusters in our Galaxy. To understand the metallicity distribution and gradient of the LMC, we estimated a metallicity map using the red giant branch (RGB) stars, from the Magellanic Cloud Photometric Survey (MCPS) and Optical Gravitational Lensing Experiment (OGLE III) photometric data. This is a first of its kind map of metallicity up to a radius of 4 - 5 degrees, with good sampling of the bar region. The slope of the RGB is used as an indicator of the average metallicity of a subregion, and it is calibrated to metallicity using spectroscopic data for field and cluster red giants in selected subregions. The bar is found be the most metal-rich region of the LMC, and indicative of an active bar in the past. Both the data sets suggest a shallow radial metallicity gradient up to a radius of 4 kpc. This metallicity gradient of the LMC disk, though shallow resembles the gradient seen in spiral galaxies, and is also similar to that found in our Galaxy.


About Speaker: PhD Student (final year, thesis submitted) Indian Institute of Science (Joint Astronomy Porgram). Indian Institute of Astrophysics.



[161] Topic: A Study on dynamical Aspects of aerosol over the central Himalayan region

Speaker: Krishna Kumar Shukla
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-11-30
Time: 15:30hr
Venue: Auditorium

Abstract: To study the dynamical aspects of aerosols, we have utilized continuous and simultaneous datasets performed during an Indo-US collaborative project the Ganges valley aerosols experiment (GVAX) during June 2011-March 2012 over a high altitude site Manora Peak, Nainital in the central Himalayan region due to its unique topography. A detailed discussion about the dynamics and estimation of diurnal/seasonal variation of ABL height by using different methods have been done in this thesis and found that it varies between ~ 0.6-1 km, above ground level (AGL) in all the seasons. The estimation of ABL cloud base height (CBH) by using Doppler Lidar and ceilometer have been done and found good correlation R2=0.76 between both the CBH. We have studied the diurnal/seasonal variation of vertical velocity (VV) (it shows the upslope and downslope wind during daytime and nighttime respectively over the site) and VV variance (it shows the intensity of turbulence over the site). We have also observed that the aerosol optical depth is modulated with the periodicity of ~ 60-80 min (gravity wave) and with period of ~ 25-45 (Rossby wave) days dominant over the observational site. We have observed an additional atmospheric warming due to waves (Gravity and Rossby) of ~ 40 and 16 % respectively.


About Speaker: Mr. Krishna Kumar Shukla is Research Scholar in Atmospheric Science group and pursuing his PhD with Dr. D V Phani Kumar. This is a PhD pre-submission talk.



[160] Topic: PALOMA: A magnetic CV between Polars and Intermediate Polars

Speaker: Arti Joshi
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-10-30
Time: 15:30hr
Venue: Auditorium

Abstract: We present analyses of archival X-ray data obtained from the XMM-Newton satellite and optical (photometric + polarimetric) data obtained from 1.04-m Sampurnanand Telescope at Manora Peak, Nainital and 1.3-m Devasthal Fast Optical Telescope (DFOT) located at the Devasthal, both operated by Aryabhatta Research Institute of Observational Sciences (ARIES) for the candidate magnetic CV Paloma. From the X-ray data, we report two persistent periods at 156 ± 6 min and 130 ± 4 min, which we interpreted as the orbital and spin periods which are strongly indicated in the power spectrum of the time series. These periods are similar to those obtained from the optical data. The averaged X-ray spectral data obtained with EPIC-PN and MOS detectors are well fitted by a two apec component with temperatures of 0.093 +/-0.011 and 12.57 +/- 0.55 keV with an Fe Kα line and an absorbing column density of 6.1 × 10 22 cm -2 . This material partially cover 64 ± 1 % of the X-ray source. We also present the orbital and spin phase-resolved spectroscopy of Paloma in 0.3 − 10.0 keV energy range and found that X-ray spectral parameters show orbital and spin phase dependences. Details of the results are presented and discussed. These results show that Paloma belongs to a class of a few magnetic CVs that have same characteristics of both the polars and intermediate polars.


About Speaker: Ms. Arti Joshi is a fourth year Ph. D. student at ARIES.



[159] Topic: Global surface ozone observations and analyses – Insights from the WMO-GAW Programme and the TOAR

Speaker: Dr. Martin Schultz
Affiliation: Institute for Energy and Climate, Forschungszentrum Jülich, Germany
Date (yyyy-mm-dd): 2015-10-26
Time: 15:30hr
Venue: Auditorium

Abstract: Ozone is an atmospheric trace gas which is important to mankind in several regards: first, it is a harmful air pollutant affecting health and ecosystems, second, it acts as greenhouse gas and is the second or third most important radiative forcing agent, and, third, in the stratosphere it protects the life on Earth from harmful UV radiation. Due to anthropogenic activities and possibly climate change, the concentrations of ozone in the lower atmosphere have changed considerably from pre-industrial times to present. Nowadays, measured ozone concentrations near the surface are almost twice as large as when ozone was first measured reliably in the 1950s or 1960s. In the troposphere, ozone is formed through chemical reactions of multiple precursors, and because of the large variability of emissions of such precursors, ozone concentrations also vary substantially even on regional scales. The World Meteorological Organisation coordinates the Global Atmosphere Watch Programme to establish reliable, long-term measurements of trace gases and other atmospheric constituents around the globe. Together with data from various regional contributing networks, the surface ozone observations collected in GAW allow for a reasonable assessment of tropospheric ozone changes, although many world regions are still severely under-sampled. In the Tropospheric Ozone Assessment activity, a large group of international researchers attempts to analyze and synthesize all available information on tropospheric ozone and evaluate recent ozone changes. In Jülich, these activities are supported through building up the world’s largest collection of surface ozone data. These data are stored in a relational database and made available for research use through a comfortable web interface. The presentation will give an introduction to tropospheric ozone, the current measurement network, its global distribution, and the status of the TOAR database.


About Speaker: Dr. Martin Schultz, Head Global Atmospheric Modeling, Institute of Energy and Climate Research (IKE-8 Troposphere), Research Center Julich, Julich, Germany is involved in various international projects like MACC, LRTAP, GEIA, SPACR, GAW, TOAR, etc. He is also responsible for the data center of Tropospheric Ozone Assessment Report (TOAR).



[158] Topic: Proposed Spectral Collocation of a Multi-Mode Solar Dynamo

Speaker: Prof. Steven Pearce
Affiliation: Simon Fraser University, British Columbia, Canada
Date (yyyy-mm-dd): 2015-09-30
Time: 15:30hr
Venue: Auditorium

Abstract: This talk will review the current state-of-affairs concerning solar dynamo theory. A recent sensationalized publication by Professor Valentina Zharkova has prompted a concerted effort to produce an accurate spectral collocation MHD simulation in order to demonstrate the feasibility of a mult-mode dynamo process in the convective layer of the sun. As such, we will review of the Grand Minima Problem and provide a brief review of our spectral collocation technique and provide an illustrative geodynamo model calculation recently announced at the Wessex Institute demonstrating the advantages of this method.


About Speaker: Prof. Steven Pearce is faculty in Simon Fraser University, British Columbia, Canada. Now a days he is visiting faculty at Indian Institute of Information Technology (IIIT), Allahabad.



[157] Topic: Study of tropospheric trace gases over the Indian subcontinent

Speaker: Piyush Bhardwaj
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-09-24
Time: 15:30hr
Venue: Auditorium

Abstract: Surface based observations of O3, CO, light NMHCs and BC were made during the international field campaign SusKat-ABC during Dec 2012–June 2013 in the Kathmandu valley and surrounding regions. The diurnal variations at Bode were typical of a polluted urban site with sharp day time build up in O3, and CO having higher levels during morning/evening hours. The early morning CO levels were higher during winter (Jan-Feb, ~ 1500 ppbv) than spring (Mar-May, ~1100 ppbv). However, daytime O3 levels were slightly higher during spring (~62 ppbv) when compared with those during winter (~54 ppbv). High resolution WRF-Chem setup was done over Kathmandu valley (9, 3, 1 km). Large differences in the meteorological parameters were observed with nightime differences being the highest. Differences in temperature and RH were ~1 oC, 10% during daytime and 4-8 oC, 40-60% during night-time respectively. Wind speeds and directions were in good agreement. Model was warm and drier during night time and was unable to capture fog at night. The day and night-time differences in O3 were ~25 and ~50ppb respectively and CO showed even larger day/night differences 100-200 ppb during daytime and 500-1500 ppb at night. These differences improved with some modifications in model but still large differences were observed at Bode. The similar differences in meteorology at a mountain top Nagarkot was much lower (<10%) and model performed well there.


About Speaker: He is a 5th year Research Scholar.



[156] Topic: Time variability and physical properties of AGN.

Speaker: Prashanth Mohan
Affiliation: ARIES, Nainital
Date (yyyy-mm-dd): 2015-09-15
Time: 15:30hr
Venue: ARIES AUDITORIUM

Abstract: Variability in active galactic nuclei (AGN) spans a wide range of timescales from a few 100 s (gamma rays) to a few years (optical and radio). Here, we present recent models and constraints on the AGN jet properties and black hole mass. We first study the effects of radiation pressure and drag which stabilize the outflow with Lorentz factors of 1.1 - 7, used as inputs to a model of jet based variability. Then, we describe the radio core shift effect in blazar 3C 454.3 using the 4.8 GHz - 36.8 GHz long term radio light curves. We infer a magnetic field strength of 0.07 - 1.43 G at 1 pc and 0.03 - 0.17 G at the core. A Fourier periodogram analysis yields power law slopes ranging between -1.6 and -3.5, and gives bend timescales ranging between 0.52 and 0.66 yr. Flares originate from multiple shocks in a region at a distance of a few to tens of parsecs from the central region. We then study the ~ 1.6 yr Kepler light curve of the blazar W2R 1926+42. A bend timescale of 3.1 - 12.6 hours is inferred. Using this and the normalized excess variance, we infer a black hole mass of (1.5 - 5.9) x 10^7 M_sun. We argue that the observed variability and an inferred weak and short duration quasi periodic oscillation could be due to jet based orbital features and others such as shocks and turbulence.


About Speaker: He is PDF at ARIES.



[155] Topic: Study of Aerosol characteristics over central Himalayas

Speaker: Ms Hema Joshi
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-09-11
Time: 15:30hr
Venue: Auditorium

Abstract: Multiyear measurements of aerosols are studied over the central Himalayas in view of the crucial role played by aerosols in climate change, radiation budget, and air quality. The ground based aerosol measurements over the central Himalayan region were utilized to understand aerosol variability and trends at a high altitude site, while the first time absorbing aerosols characterization was made at a low altitude semi urban site in the Indo-Gangetic Plain (IGP) region, adjacent to Himalayan foothills. The ground based examination of aerosols are complemented by space-borne sensors to explain and discuss the surface, columnar, and vertical distribution of aerosols over this region. The roles of meteorological processes such as boundary layer dynamics, convection, regional and long-range transport along with possible sources of aerosols, their seasonality and processes governing the observed concentration or loading are discussed in detail. The aerosol characterization over this region is also discussed in context to other locations. The current state of the science of chemical transport model known as the Weather Research and Forecasting Model coupled with Chemistry (WRF-Chem) was examined for absorbing aerosol, BC. Further, it is shown that agricultural crop residue burning in northern India significantly affects the aerosol load in the central Himalayas which has implications for the atmospheric thermodynamics in this region. These investigations carried out here further motivated to identify the source types of these aerosols and their seasonality in detail. The multiyear data is proposed to use to the source apportionment and estimating aerosol impacts.


About Speaker: She has applied for the RA under a ISRO project.



[154] Topic: Investigating supernovae and probing its CSM

Speaker: Mr Subhash Bose
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-09-04
Time: 15:30hr
Venue: Auditorium

Abstract: We characterized a number of core-collapse supernovae events which has been extensively observed in photometric, spectroscopic and polarimetric modes at optical wavelengths. Our primary goal was to understand various mechanisms involved in the explosion and how they govern observable parameters. We utilized the observational data to constrain progenitor properties, explosion parameters and also to probe circumstellar environment to infer their pre-SN evolution which the progenitor might have undergone. We also probe various peculiarities these SNe exhibits in their observed light curves and spectra. In this talk I shall briefly summarize the key aspects which I investigated in my thesis and shall discuss the scope of further work which I propose to do. Expanding photosphere method (EPM) has been demonstrated to be a reliable distance estimator at extragalactic scale. It would be interesting to extend the work to higher redshift SNe, which would require few epoch of observations during the first month of explosion. Apart from astronomical importance of the estimated distances, it can be used to construct Hubble diagram having a sample of sufficiently high-z SNe. Probing the circumstellar interaction is also a key proposed idea of my future work, which may reveals a wealth of information about the history of pre-SN stellar explosion. As in SNe IIn, where profound interaction occurs between ejecta and extended dense shell of material originated from mass loss of massive WR type progenitors during its stellar life. The study of these interactions give information about the environment and progenitor when the mass loss of the shell happened back in time. Additionally I shall also investigate type IIL or fast declining events to answer some of interesting question which arose from my thesis work. The prevalence of CSM interaction in SNe IIL and its connection with unusual flattening of of HI velocity are also to be examined on more of such events.


About Speaker: He has submitted his PhD thesis and has applied for the PDF position at ARIES.



[153] Topic: Investigating the Behaviour of Exploding Stars

Speaker: Mridweeka Singh
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-08-27
Time: 15:30hr
Venue: Auditorium

Abstract: Supernovae are the dominant sources of stellar feedback, which plays an important role in regulating galaxy formation and evolution. They are widely recognized as end stages of stellar evolution. During the previous three observing seasons from October 2014 to June 2015 we observed a number of events covering various subtypes of SNe such as Ia, Ib and IIP starting from nearly 10 days after discovery and lasting upto approximately 200 days. Amongst these we present preliminary light curve and color curves of a type Ib event M12045 in NGC 4080. We compare the absolute magnitudes of M12045 with other Ib SNe. An early time spectrum at +12 days is also presented and shows the prominent He feature typical of Ib SNe.


About Speaker: She is 2nd year Research Scholar and pursuing PhD with Dr. Kuntal Mishra



[152] Topic: Study of Galactic Star Forming Regions and related Instrumentation

Speaker: Neha Sharma
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-08-27
Time: 14:30hr
Venue: Auditorium

Abstract: To obtain the polarization due to the dust grains that are present in the cloud, it is essential to subtract the polarization due to those that are present foreground to the cloud. The polarization vectors of foreground subtracted 186 stars are over-plotted on the WISE 12m image as shown in Fig. 1. The mean values of P% after the subtraction of the fore- ground interstellar polarization is obtained as 1.5 %. The mean value of P is found to be 40 which is considered as the mean direction of the plane of the sky component of magnetic eld in Gal 110-13. Based on far-infrared, HI and CO data of the region, Odenwald et al. (1992) proposed cloud-cloud collision scenario to be the most preferred mechanism responsible for the formation of Gal 110-13. They suggested that the Gal 110-13 was formed as a result of the interaction between two HI clouds moving across the line of sight and having velocity components of 􀀀8 and 􀀀6 km s􀀀1. They also suggested that the southern part compared to the northern part is in an advanced stage which resulted in it being predominantly molecular. According to Odenwald et al. (1992), based on HI observations, collided clouds have traveled across the line of sight in the northeast􀀀southwest direction. But the current magnetic eld geometry is almost perpendicular to the proposed direction of the interaction of the clouds. Also, the simulations show that irrespective of the initial eld con guration, in both parallel and perpendicular cases the eld distribution after the shock interaction was found to be chaotic especially on the large scales (Marinho et al., 2001). However, the observed magnetic eld lines from polarization are found to be uniformly distributed contrary to the results from the simulations. Lee and Chen (2007) have considered either a supernova explosion or ionization fronts from a massive star in the vicinity of Gal 110-13 as alternate mechanism that might have caused its cometary shape.


About Speaker: She is a 3rd year research scholar and pursuing PhD with Dr. Maheswar Gopinathan



[151] Topic: Co-spatial Photospheric enhancement and H alpha evolution of the X-class flare

Speaker: Aabha Monga
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-08-26
Time: 14:30hr
Venue: Auditorium

Abstract: My work includes the evolution of the Flare and the active region AR11748 where the X1.2 class are is observed on May 15, 2013 with the magnetic complexity . The active region was spread in the area of 310 km2 in the North-Eastern limb of the Sun. I have analyzed the region and are with different wavelength data sets to nd its evolutionary behavior. Flare shows the two ribbon structure and I also found that stationary brightening propagates along the southern ribbon. On the contrary, I found the emerging material from the same region was the driver of the instability. I did not nd the any lament associated with the are. For the morphological evolution of the active region, I have used SDO data and I have used SDO/HMI magnetograms and the velocity Dopplergrams for the photospheric magnetic parameters. From this study, I conclude that are occurred in the lower corona and the coronal loops moved upward which gives the signature of the magnetic reconnection beneath the uprising loops.


About Speaker: She is 3rd year Research Scholar and pursuing PhD with Dr. Wahab Uddin.



[150] Topic: Star Formation Aspect in Different Environments of Star Forming Galaxies

Speaker: Abhishek Paswan
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-08-26
Time: 16:30hr
Venue: Auditorium

Abstract: We present our annual report on studied works whi h have been arried out during the session 2014-2015. Our work omprises mainly the study of star formation rates (SFRs) in nearby star- forming galaxies at their di erent evolutionary stages su h as galaxies belong to the blue loud (late-type with re ent star formation) and red sequen e (early-type with residual or suppressed star formation). Hen e regarded these points we have studied a sample of Wolf-Rayet galaxies from Brin hmann et al. (2008) atalogue showing re ent star formation events using H narrow- band imaging from 1.3-m Devasthal opti al teles ope. For these galaxies, we also used spe tros opi data from SDSS survey in order to make several orre tions to the observed H ux and to derive more other related physi al parameters from the spe trum of galaxies. In addition, we have also studied a volume-limited sample of blue early-type galaxies taken from S hawinski et al. (2009) atalogue showing residual or suppressed star formation events using 1.4 GHz radio ontinuum data from the VLA FIRST survey along with opti al data from the SDSS survey.


About Speaker: He is a 4th year Research Scholar and pursuing PhD with Dr. Amitesh Omar.



[149] Topic: Study of magnetic activities on late-type stars

Speaker: Subhajeet Karmakar
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-08-24
Time: 15:30hr
Venue: Auditorium

Abstract: The solar-type stars shows rich variety of magnetic activities such as surface inhomogeneities due to presence of dark spots, short and long-term variations in spot-cycles and flares. Using the wealth of ∼24 yr multi-band data, we present an in-depth study of the evolution of starspot distributions, optical-flares, Surface Differential Rotations (SDR) and coronal activities on the surface of young, single, main-sequence, Ultra Fast Rotator (UFR) LO Peg. With V-band data a rotational period of 0.422923 ± 0.000005 d has been established. In our study for the first time we have investigated the long-term periods of LO Peg. Evidence of existence of three periods of ∼2.98 yr, ∼7.44 yr and ∼11.8 yr have been detected. Using the seasonal variations on rotational period we also investigate the SDR pattern. LO Peg shows a solar-like pattern of SDR, that is the rotational period steadily decreases along the activity cycle, jumping back to higher values at the beginning of the next cycle with a cycle of 2.8 yr. During the observations 20 optical flares are detected with a derived flare frequency of ∼1 flare per two days. Energies of these flares have been found to vary within a range of 10^{32−34} erg. Using light curve inversion technique (iPH code) we have constructed temperature inhomogeneity map of the surface of LO Peg. The surface coverage of cool spots is found to be in the range of ∼6-27%. It appears that the high and low latitude spots are interchanging their positions. Using XMM-Newton observation, we investigate properties of a flare from the very active and poorly known stellar system 47 Cas. The luminosity at the peak of the flare was found to be 3.54 × 10^30 erg s^{−1} , which is ∼2 times more than that at quiescent state. The quiescent state corona of 47 Cas was represented by two temperature plasma: 3.7 and 11.0 MK. The time-resolved X-ray spectroscopy of the flare showed the variable nature of the temperature, the emission measure, and the abundance. The maximum temperature during the flare was found to be 72.8 MK. We inferred the length of a flaring loop to be 3.3 × 10^10 cm using a hydrodynamic loop model. Using ∼11 years XMM-Newton data we present flare analysis of a young, main-sequence ultra-fast rotator AB Dor. A total of ∼140 X-ray flares were detected in the entire span of observations. Evidence of two temperature quiescent corona at 3.36 MK and 11.1 MK is seen. The density of each flare is derived at the range of 2-10 X 10^10 cm^{−3} . The flaring loop length is found to vary in the order of 1010 cm.


About Speaker: He is a 4th year Research Scholar and pursuing PhD with Dr. Jeewan C pandey.



[148] Topic: A search for the elusive radio-quiet BL Lacs

Speaker: Parveen Kumar
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-08-26
Time: 15:30hr
Venue: Auditorium

Abstract: The Sloan Digital Sky Survey (SDSS) and Two-Degree Field QSO Redshift Survey (2QZ) have revealed a population of Active Galactic Nuclei (AGNs) with peculiar spectral characteristics. These objects have featureless optical discovery spectra resembling BL Lac objects. However, they are significantly quiet in radio and X-ray bands compared to classical BL Lacs. These objects could therefore belong to the hitherto unrecognized population of radio-quiet BL Lacs or radio- quiet quasars without a Broad Line Region (BLR). How such objects fit into the AGN unification picture is an open question. Polarization and variability are the two main characteristic properties of BL Lac objects. Last year, I was involved in two such project,first one is polarisation and spectroscopy study of radio-quiet BL Lacs. Therefore, we selected a sample of 19 radio quiet BL Lacs, from 2QZ and SDSS to study their polarisation, optical variability and spectroscopy. Polarimetric and spectroscopic observations of these 19 radio quiet BL Lacs were carried out using the 3.6m telescope at European Southern Observatory (ESO La Silla, Chile). Here we found optical polarisation around ∼ 1% for our this sample. We did not find high polarisation (P > 3%), like BL Lacs in our sample of radio quiet BL Lacs objects. Regards spectroscopy, we found weak emission line in few sources. It is may be due to small sample to detect such a rare class of AGN, radio-quiet BL Lacs. To find such a rare class, a good sample is needed. We have a sample of ∼ 40 radio-quiet weak emission line quasars with intranight optical variability (INOV) observations and it would be very interesting if we found BL Lacs like polarisation in these objects. Second is continuation of our search for the elusive radio-quiet blazars, by carrying out a systematic programme to detect intranight optical variability (INOV) in a subset of ‘Weak-Lines- Quasars’ (WLQs) which are designated as ‘high confidence BL Lac candidates’ and are known to be radio-quiet. For 19 such RQWLQs, we present here the INOV observations taken in 40 sessions of durations ≥ 3.5 hours each. The 40 differential light curves (DLCs), thus obtained for the 19 RQWLQs, were subjected to an statistical analysis using the F−test and the deduced INOV char- acteristics of the RQWLQs are compared with those published recently for several prominent AGN classes, also using the F−test. However, since the RQWLQs are generally 1−2 magnitudes fainter, a rigorous comparison has to wait for somewhat more sensitive INOV observations than those pre- sented here. Based on our existing INOV observations, it seems that RQWLQs in our sample show a significantly higher INOV duty cycle than radio-quiet quasars and radio lobe-dominated quasars. Two sessions, when we detected rather strong (blazar-like) INOV for RQWLQs are pointed out and both these RQWLQs are therefore candidates for radio-quiet BL Lacs.


About Speaker: He is a 3rd year Research Scholar and pursuing PhD with Dr. Hum Chand.



[147] Topic: Multi-wavelength study of Magnetic Cataclysmic Variables (CVs)

Speaker: Arti Joshi
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-08-24
Time: 16:30hr
Venue: Auditorium

Abstract: We present analyses of archival X-ray data obtained from the XMM-Newton satellite and op- tical (photometric + polarimetric) data obtained from 1.04-m Sampuranand telescope (ST) at Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital and 1.3-m Devasthal Fast Optical Telescope (DFOT) located at the Devasthal, Nainital for the candidate magnetic CV Paloma. From the X-ray data, we report two persistent periods at 156±6 min and 130±4 min, which we interpreted as the orbital and spin period which are strongly indicated in the power spectrum of the time series. We also interpreted Paloma is a key object for magnetic CV evolution with an orbital period right within the period gap. Photometric and Polarimetric observations of ten mag- netic CVs were also carried out in 84 nights from ST and DFOT at ARIES , among all these CVs we present the photometric results of the five candidates 2MASSJ0130+6221, 2MASSJ0345+5335, RXJ0749-0549, RXJ0859+0537 and 1RXSJ1858+4914. Three of the systems 2MASSJ0130+6221, RXJ0749-0549 and RXJ0859+0537 was found to be eclipsing from photometric data and have orbital periods above the CV period gap of 2-3 h.


About Speaker: She is 3rd year Research Scholar and pursuing PhD with Dr. Jeewan C pandey.



[146] Topic: A Study on Dynamical Aspects of Aerosols over the Central Himalayas

Speaker: Krishna K Shukla
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-08-21
Time: 14:30hr
Venue: Auditorium

Abstract: During the Indo-US collaborative Ganges Valley Aerosol Experiment (GVAX), a Doppler Lidar was operated continuously from June 2011 - March 2012 at a high altitude site Manora Peak (29.4o N; 79.2o E; 1958 m, amsl) in the Himalayan foothills. The Doppler Lidar provides height-resolved measurements of vertical velocity and attenuated backscatter over the site. Doppler Lidar and Multi Filter Rotating Shadow band Radiometer (MFRSR) observations are utilized to show wave like signatures in AOD during daytime atmospheric boundary layer (ABL) evolution over the Himalayan region. Fourier analysis depicted 60-80 min periods dominant during afternoon hours, implying that the observed modulations could be plausible reason for the AOD forenoon-afternoon asymmetry which was previously reported. Inclusion of wave amplitude in diurnal variation of aerosol radiative forcing estimates showed ~40% additional warming in the atmosphere relative to mean AOD. We also investigate diurnal and seasonal variation of vertical velocity and attenuated backscatter below 1 km, AGL during the post-monsoon (September-November), winter (December-February) and pre-monsoon (March) seasons. The vertical velocities exhibit a strong diurnal pattern throughout the observational period depicting upslope flows during daytime and down slope flows during nighttime. The magnitude of the vertical velocity varies between 0.1-0.4 m.s-1 in all seasons. The vertical velocity variance ranges from 0.2-1.5 m2s-2 and was found to be higher during daytime due to strong convection followed by a decrease during nighttime due to cooling at the surface. The magnitude of attenuated backscatter varies between -6.5 and -5 m-1sr-1 (represents log10 scale) in all seasons. We also investigated the impact of variable weather conditions on vertical velocity and the results are discussed in the light of the current understanding of the boundary layer dynamics over the observational site.


About Speaker: Mr Krishna K Shukla is pursuing Ph D with Dr. D V Phani Kumar.



[145] Topic: Studies of Nearby Star-Forming Galaxies

Speaker: Sumit Jaiswal
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-08-21
Time: 15:30hr
Venue: Auditorium

Abstract: We have performed two surveys namely HI survey and Ha survey of a sample of WR galaxies. The main aims of this study are to see the optical and radio morphology of these galaxies and role of environment interactions in triggering the starburst in them and to find the star formation rate in the sample galaxies using Ha data and compare it with other SFR indicators. 3 We present the gray-scale Ha and R band images of few galaxies of our sample in figure 1. All the images have their north up and east left. A linear scale-length in kpc is shown at the bottom of each image. The R-band images traces the old stellar population in the galaxy and therefore it can provide the features of galaxy interactions. On the other hand, the Ha images traces the ionized gas (HII regions) and therefore it provides the distribution of star forming regions in the host galaxy with respect to the environmental effects. The clear interaction features can be seen in most of the galaxies in the sample. This result can be used to speculate that the galaxy-galaxy tidal interaction could be the main cause of massive star formation in galaxies. We also present the HI column density maps of few galaxies of our sample in figure 2. The HI column density contours are overlaid on the gray-scale DSS image. These images show a clear indication of tidal interaction in these galaxies through various asymmetries.


About Speaker: Mr Sumit Jaiswal is pursuing PhD with Dr. A Omar.



[144] Topic: Multi-wavelength studies of Blazars

Speaker: Aditi Agarwal
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-08-21
Time: 16:30hr
Venue: Auditorium

Abstract: To search for optical variability on a wide range of time scales, we have carried out photometric monitoring of two flat spectrum radi o quasars, 3C 454.3 and 3C 279, plus one BL Lac, S5 0716+714, all of which have been exhib iting remarkably high activity and pronounced variability at all wavelengths. CC D magnitudes in B, V, R and I pass-bands were determined for ∼ 7000 new optical observations from 114 nights made during 2011 – 2014, with an average length of ∼ 4 h each, at seven optical telescopes: four in Bulgaria, one in Greece, and two in India. We measured multiband optical flux and colour variations on diverse timescales. Discrete corr elation functions were com- puted among B, V, R, and I observations, to search for any time delays. We found weak correlations in some cases with no significant time lags. The structure function method was used to estimate any characteristic time-scales of vari ability. We also investigated the spectral energy distribution of the three blazars using B, V, R, I, J and K pass-band data. We found that the sources almost always follows a bluer -when-brighter trend. We discuss possible physical causes of the observed spectral v ariability. Project 2 : We monitored BL Lacertae for 13 nights in optical B, V, R, and I bands during October and November 2014 including quasi-simultan eous observations in V and R bands using two optical telescopes in India. We have studie d multi-band optical flux variations, colour variation and spectral changes in this b lazar. Source was found to be active during the whole monitoring period and showed signifi cant intraday variability on 3 nights in V and R filters while displayed hints of variabil ity on 6 other dates in R passband and on 2 nights in V filter. From the colour-magnitud e analysis of the source we found that the spectra of the target gets flatter as it becom es brighter on intra-night timescale. Using discrete correlation technique, we found that intraday light curves in both V and R filters are almost consistent and well correlated with each other. We also generated spectral energy distribution (SED) of the target using the B, V, R, and I data sets for all 13 nights which could help us investigate the phy sical process responsible for the observed variations in BL Lacertae objects. We also disc uss possible physical causes of the observed spectral variability. Project 3 (ongoing) : In this project, we study variability of ∼ 15 blazars on all three timescales using Optical/NIR photometric observati ons. We found significant flux variations in most of them. We have measured the multiband op tical flux and colour variations in these blazars on intra-day and short-term tim escales. We also plan to investigate the spectral slope variability and possible co rrelations between colour and magnitude to differentiate between FSRQs and BL Lacertae obj ects. We also plan to do cross-correlation analysis to search for time delays.


About Speaker: She is 3rd year research scholar and working with Dr Alok Gupta



[143] Topic: Radiatively driven relativistic jets with variable adiabatic index equation of state

Speaker: Mukesh Kumar Vyas
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-08-18
Time: 14:30hr
Venue: Auditorium

Abstract: We study a relativistic fluid jet driven by radiation from accretion disc around a non-rotating black hole. We compute the radiative moments with full special relativistic transformations. We show that the terminal speed of jets increases with the mass accretion rates, synchrotron emission of the accretion disc and reduction of proton fraction of the flow composition. To obtain relativistic terminal velocities of jets, both thermal and radiative driv- ing are important. We show for very high accretion rates and pair dominated flow, jets around super massive black holes are truly ultra-relativistic, while for jets around stellar mass black holes, terminal Lorentz factor of about 10 is achievable.


About Speaker: This is a review talk by Mr Mukesh, who has completed 2nd year.



[142] Topic: Innermost structure of quasars using optical interferometry and reverberation mapping

Speaker: Suvendu Rakshit
Affiliation: OCA, Nice, France
Date (yyyy-mm-dd): 2015-08-20
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: The broad line region (BLR) of Active Galactic Nuclei (AGN) contains the high velocity gas clouds transporting material from the dust torus to the accretion disk around the central super massive black hole (SMBH). Unveiling BLR structure is critical to understand the accretion mechanism driving the SMBH evolution and shaping the AGN inflows, outflows and jets. Reverberation Mapping (RM) constrains the BLR geometry, kinematic, mass and equivalent linear size with parameter degeneracies and fudge factors depending from the source geometry. Optical Interferometry (OI) yields independent constrains on BLR structure, mass and equivalent angular size. We developed a 3D geometrical model of BLRs to estimate both RM and OI measures and to show that the combination of these two techniques will very substantially reduce the uncertainty of mass estimates and yield direct distance measurement from quasar parallax. We used this model and a Monte Carlo Markov Chain Bayesian parameter fit of simulated data to show that quasar parallax can measure distances with accuracy better than 16%. We used it on actual data to interpret and explain our first OI observations of the BLR of the bright quasar 3C273 found to have a BLR of about 1750+/-35 light days (ld) much larger than predicted by RM (450+/-120 ld) and larger than the inner rim of the dust torus of about 800+/-270 ld, yielding a SMBH mass of (5+/-1) 10^8 solar masses. Our model and SNR computations show that the VLTI incoming instruments can observe about 60 BLRs covering more than 4 decades of luminosity, enough to try a grand unification of BLRs models and a calibration of RM making QSOs major cosmological probes.


About Speaker: Ph.D from OCA, Nice, France



[141] Topic: Multiwavelength investigation of Core-Collapse supernovae

Speaker: Mr Subhash Bose
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-08-17
Time: 15:30hr
Venue: Auditorium

Abstract: Supernovae (SNe) are one of the most energetic cosmic events in the universe and they are prime candidates responsible for heavy element enrichment in present universe. The study of these exotic events are fascinating in itself. Core-Collapse supernovae (CCSNe) are the end fate of massive stars with wide range of properties and so the observable parameters of these explosions are also very diverse. Circumstellar environment and history of pre-SN evolution also plays a key role in diversifying their properties. In this thesis we characterize a number of CCSNe events which has been extensively observed in photometric, spectroscopic and polarimetric modes at optical wavelengths. This thesis utilizes data collected primarily from telescopes in India viz. 104cm ST and 130cm DFOT at ARIES, 2mIGO at IUCAA and 2mHCT at IIA. Complementary data were also collected from several international network of telescopes and Swift UVOT observations. Our primary goal was to understand various mechanisms involved in the explosion and how they govern observable parameters. We utilized the observational data to constrain progenitor properties, explosion parameters and also to probe circumstellar environment to infer their pre-SN evolution which the progenitor might have undergone. We characterize five CCSNe events (SNe 2012aw, 2013ab, 2013ej, 2013hj and 2014G) in detail. Along with the determination of various physical parameters by modeling the observables, we also probe peculiarities which they exhibit in their observed light curves and spectra. Our detailed observations and spectroscopic modelling revealed ejecta-CSM interaction in SNe 2012aw and 2013ej, and also signature of emergence of recombination phase for the first time in SNe II. Such detections are crucial to improve our understanding of these event. Another vital component of this thesis is utilizing type II SNe as a distance estimator, which has immense cosmological as well as astronomical importance. SNe due to high intrinsic brightness are always an attractive probe for extragalactic distance measurements, however SNe II require an approach which is entirely different than standard candle methods. We implement Expanding photosphere method (EPM) to estimate distances to host galaxies of eight type II SNe and also introduce some improvements in the existing methodology. Our study explored various issues and uncertainties involved in EPM and also demonstrated its potential as a reliable redshift independent technique.


About Speaker: This is a pre-submission talk of PhD thesis work.



[140] Topic: Interstellar Dust and its Modeling

Speaker: Ranjan Gupta
Affiliation: IUCAA
Date (yyyy-mm-dd): 2015-08-18
Time: 15:30hr
Venue: Auditorium

Abstract: Its is well known that the interstellar dust plays the most important role in which the light seen form stars suffers extinction. Conventional models assume Mie theory of light scattering with solid spheres and other shapes of silicate and graphite particles of different sizes. An extension of this theory was Effective Medium Theory (EMT) which tries to explain some of the observed interstellar properties. Recent space probes have confirmed that the dust grains are highly porous and fluffy (i.e. aggregates or clusters) rather than having regular shapes (spherical, cylindrical or spheroidal) and homogeneous in compositionand structure. Since their is no exact theory for calculation of scattering properties of such irregular, inhomogeneous particles, recently our group has used Discrete Dipole Approximation (DDA) method and the results of this investigation will be discussed. The model uses a composite fluffy dust grain for explaining most of the average observed interstellar extinction curves and also polarization. Another parameter which needs to be constrained by the dust models is the interstellar abundances of Carbon and Silicon which is usually overestimated by the solid dust models but ourmodel predicts closer match to the observed ISM abundances. Recently, we have used our composite dust model to characterize the dust properties in about 50 different directions in our galaxy. The Silicate dust emission features at 10 and 18 microns is also explained by our composite grain model which helps in understanding the dust characteristics in the circumstellar dust shells around stars.


About Speaker: Ranjan Gupta is a senior professor at IUCAA



[139] Topic: The HIF/Photosphere Interactions in Cepheids and RR Lyraes and multi-phase PL/PC Relations

Speaker: Prof. Shashi M. Kanbur
Affiliation: Department of Physics, State University, New York
Date (yyyy-mm-dd): 2015-08-11
Time: 15:30hr
Venue: Auditorium

Abstract: We provide strong empirical evidence for a nonlinearity in the Cepheid Period-Luminosity (PL) relations at a number of wavelengths using Galactic, LMC and SMC multi-wavelength data from published sources. We provide a possible theoretical explanation for this that involves the interaction of the stellar photosphere and hydrogen ionization front and show that this has implications for Period-Color and Amplitude-Color (PCAC) relations as well. We extend our analysis to look for nonlinearities in PCAC relations for RR Lyraes. We show the importance of considering the way PL/PC relations vary as a function of period and phase and discuss the implications for stellar modeling, the extra-galactic distance scale and estimate of Hubble constant.


About Speaker: Shashi Kanbur is Professor and Chair at Department of Physics at State University of New York



[138] Topic: Identification of YSOs and star formation scenario in the Auriga Region

Speaker: Vinay Tripathi
Affiliation: IIT Delhi
Date (yyyy-mm-dd): 2015-07-24
Time: 15:00hr
Venue: Auditorium

Abstract: This work presents a multiwavelength study of the Auriga region. It includes the investigation of the evolutionary stages, disk properties and other parameters like Temperature, Mass etc. of Young Stellar Objects (YSOs) across the Auriga region by modeling the broadband optical to mid-infrared (MIR) Spectral Energy Distributions (SEDs). The YSOs are classified into different classes based on the parameters determined from their SED response (Robitaille et al.,2007) and are then being compared with the Classes obtained from near infrared (NIR) to mid infrared (MIR) spectral indices α to test the robustness of the SED model. Mass and age of the YSOs calculated from the modeling has been compared with the values obtained from optical Color Magnitude Diagram analysis. The spatial distribution of Class I & FLAT class predicts triggered star formation.


About Speaker: IIT Delhi MSc Student doing summer project at ARIRES



[137] Topic: On the nature of extragalactic magnetic fields from Faraday rotation measure

Speaker: Ms Vidushi
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-07-24
Time: 10:30hr
Venue: Auditorium

Abstract: We have investigated the dependance of the residual rotation measure (RRM) on the intervening Mg ii absorber at cosmic distances, by using a large sample of 340 quasars with 518 Mg ii absorbers and 565 quasars without Mg ii absorbers from SDSS and most updated quasar catalog for RM around 21cm wavelength. After discounting the contribution of foreground galactic rotation measure (GRM) of milky way, the residual rotation measure (RRM) of these quasars is used to calculate the excess extragalactic contribution in the standard deviation of the distribution of observed RRM. The excess standard deviation of the sample with intervening Mg ii absorber of about 47.53 ± 0.52 rad m−2 is found in comparison of the sample without Mg ii absorber. Our results suggest that intervening absorbers could contribute in enhancement of RRM at around 21cm wavelength, with a sample which is about twice the largest sample used in literature till now. We have also obtained the evolution of RRM with redshift, which gets saturated at higher z  3 with no Mg ii absorber. It supports the conclusion that magnetic field strength traced by RRM for high redshift galaxies is atleast comparable to the current epoch. The evolution of RRM with redshift also shows that dispersion in RRM is higher for the sample with Mg ii absorber as compare to the sightlines without Mg ii absorber.


About Speaker: She is a first year student at ARIES. This presentation is based on her project work as a part of PhD Course Work.



[136] Topic: IMAGE QUALITY OF 3.6 m OPTICAL TELESCOPE

Speaker: Anisha
Affiliation: Panjab University, Chandigarh
Date (yyyy-mm-dd): 2015-07-20
Time: 12:00hr
Venue: auditorium

Abstract: The 3.6m Devasthal optical telescope is being installed at Devasthal, Nainital, and it will provide seeing limited observational capabilities at visible and near infrared bands. The image quality of any optical telescope is very crucial to determine accurate physical properties of celestial objects and it can go bad due to variety of reasons such as poor alignment of optics and the environment of telescope.The aim of the project deals with the detection of wavefront distortion induced by misalignment of optics and other imperfections in telescope using Shack Hartmann wavefront sensor. Using modal wavefront reconstruction approach, the distorted wavefront has been reconstructed for 3.6m telescope in terms of Zernike modes and a value of RMS wavefront error of 184nm has been obtained. PSF and MTF of the image are also extracted using these Zernike coefficients. The values obtained are consistent with the image quality specification of the telescope.


About Speaker: Ms Anisha is M.Sc. (Physics) 1st year student at Panjab University, Chandigarh. Ms. Anisha did project work for 2 months at ARIES under Summer Research fellowship program-2015 of Indian academy of Sciences.



[135] Topic: SENSITIVITY OF 3.6m DEVASTHAL OPTICAL TELESCOPE

Speaker: Anusree Devanand
Affiliation: Amrita Vishwa Vidyapeetham, Kerala
Date (yyyy-mm-dd): 2015-07-20
Time: 12:30hr
Venue: auditorium

Abstract: The 3.6m optical telescope, currently the largest optical telescope in India is being built at Devasthal with an aim to develop an observational facility with spectral and seeing limited imaging capabilities at visible and near infrared bands. Electromagnetic radiation received on Earth are the major carriers of cosmological information. The ability of a telescope to collect the least possible signal describes its sensitivity. The aim of the project was to characterize the photometric and spectroscopic sensitivity of this telescope. A measure of sensitivity is given by the signal to noise ratio of the telescope. The signal to noise ratio for imaging as well as spectroscopy at various zenith angles and observing conditions has been calculated using MATLAB. In imaging, a signal-to-noise ratio of 3.9 has been obtained for a 25 mag point source in V band, measured at zenith for an exposure time of 30 minutes, using a 4KX4K CCD camera with a pixel size of 15 microns,three days from New Moon. And, in spectroscopy, a signal to noise ratio of 7.5 has been obtained for a 20 mag point source at 0.5 µm, measured at zenith for an exposure time of 10 minutes.


About Speaker: Ms Anusree Devanand is M.Sc. (Physics) 1st year student at Amrita Vishwa Vidyapeetham, Kerala. Ms. Anusree did project work for 2 months at ARIES under Summer Research fellowship program-2015 of Indian academy of Sciences.



[134] Topic: Physical state of 21-cm absorber at z_abs ~ 0.3 towards a radio-loud quasar J1443+0214

Speaker: Ms. Avni Parmar
Affiliation: Pune University
Date (yyyy-mm-dd): 2015-07-20
Time: 11:30hr
Venue: ARIES Auditorium

Abstract: Understanding the physical state of the interstellar medium of protogalaxy at high redshift plays a key role in our understanding of galaxy formation. Although it is not possible to directly observe the highly redshifted galaxies, but their signature as absorption line in the background quasar spectrum allow us to study them in both optical and radio regions. The 21-cm line, caused due to the hyperfine splitting in Hydrogen atom, is the signature of cool gas present in the interstellar medium (ISM) of this highly redshifted galaxy. In this regard we study the quasar-galaxy pair (QGP) J1443+0214 with z_qso =1.82, z_abs = 0.3714, by searching for the 21-cm HI absorption at the redshift of foreground galaxy. We use the GMRT archival spectral data centered around 1041.68 MHz with 4.17 MHz bandwidth and process it using Astronomical Image Processing System (AIPS) to obtain HI 21-cm absorption line. We find a very prominent HI absorption at the redshift of foreground galaxy (z_abs = 0.3714),thus concluding that a cool gas phase of ISM is present in this galaxy, estimate the optical depth and spin temperature of HI.


About Speaker: Ms. Avni Parmar a M.Sc final year student of Pune University is Indian Academy Summer Fellow at ARIES.



[133] Topic: Wavelength Dependence of diffuse-to-global and diffuse-to-direct spectral irradiance over Gangetic Himalayas region

Speaker: Ms. Kanika Pandey
Affiliation: Banasthali University, Rajasthan
Date (yyyy-mm-dd): 2015-07-03
Time: 15:30hr
Venue: Auditorium

Abstract: Continuous measurements of solar spectral radiation using the Multi-filter Rotating Shadow Band Radiometer (MFRSR) were performed at Nainital a high altitude location in the central Gangetic Himalayan region. The present work utilizes two clear-sky days of continuous observations from local sunrise to local sunset, in order to investigate the daily variation of the solar radiation components (diffuse, global and direct-beam) as well as their ratios (diffuse-to-global: DGR; and diffuse-to-direct beam, DDR).


About Speaker: She is MSc Final Year Student, working as a summer training program.



[132] Topic: Instrumentation: CCD and telescope

Speaker: Anjali Lohani
Affiliation: Amity University, Noida
Date (yyyy-mm-dd): 2015-06-26
Time: 12:15hr
Venue: Auditorium

Abstract: The aim of this project is to gain a first hand knowledge of instruments such as CCD and telescope being used in current astronomy. In this project, I have learnt the basic properties of telescope along with a hands on practice with CCD data.


About Speaker: The Speaker is currently enrolled in MSc (1st year) of Amity University, Noida. She is a summer project student here under Dr. Biman J. Medhi.



[131] Topic: Probing the Universe with Cosmic Microwave Background Radiation

Speaker: Prof. T. R. Seshadri
Affiliation: Delhi University
Date (yyyy-mm-dd): 2015-06-26
Time: 15:30hr
Venue: Auditorium

Abstract: Cosmic Microwave Background (CMB) is the cleanest signal from the early phase of the universe. One believes this is intrinsically isotropic, un-polarized and has a blackbody spectrum. Hence any deviation from these features provides a very good handle to understand the physical phenomenon both at the surface of last scatter and after that epoch as the photons of CMB travels towards us. The talk will essentially highlight some of the physical processes in the Universe which can produce these deviations.


About Speaker: Prof. T. R. Seshadri is senior professor at the Physics and astrophysics department of Delhi University.



[130] Topic: Characterization of Atmospheric Surface Layer Parameters during Lightning Conditions

Speaker: Arun Kumar Dwivedi
Affiliation: BIT MESRA, Ranchi
Date (yyyy-mm-dd): 2015-06-17
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: Lightning is the most beautiful as well as dangerous phenomenon appearing in nature. As this is a natural event, it cannot be stopped but some attempts are necessary which may enable us to minimize its disastrous effects. The observational site of this study is BIT Mesra, Ranchi, Jharkhand which lies in the eastern part of India. In my Ph.D. thesis, the behaviours of Atmospheric Surface Layer (ASL) parameters during lightning conditions have been observed. Flux analysis and spectral analysis of these parameters have done during lightning conditions. Based on this, an attempt has been made to develop a model to forecast the lightning occurrence during pre- monsoon season over this region. Artificial Neural Network (ANN) is used to forecast lightning. The results showed that the ANN can be used as an efficient tool for lightning forecasting over this region during pre-monsoon season. Apart from ASL parameters, vertical structure of lower atmosphere is also evaluated using radiosonde data on lightning days and a comparison has been made with the observations during clear days.


About Speaker: Mr. Arun Dwivedi has applied for the PDF position at ARIES.



[129] Topic: Magnetic field geometry of an unusual cometary cloud G110-13

Speaker: Neha Sharma
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-05-26
Time: 15:30hr
Venue: Auditorium

Abstract: Gal110-13 is an isolated, unusually elongated comet-shape cloud, which is considered as an example of star forming region resulting from cloud-cloud collision. We carried out optical polarimetry of G110-13 to understand the importance of magnetic field in the formation and subsequent star formation of G110-13. We compare our results with those from various simulations for cloud-cloud collision and ionization induced cloud evolution and discuss the most preferred mechanism with respect to the magnetic field geometry.


About Speaker: Ms. Neha Sharma is a SRF at ARIES



[128] Topic: A Little Big-bang

Speaker: Prof. Binoy Patra
Affiliation: IIT Roorkee
Date (yyyy-mm-dd): 2015-06-11
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: Quantum chromodynamics (QCD) is one part of the modern quantum field theory of particle physics which describes the interactions among quarks and gluons. At sufficiently high densities and/or temperatures the quarks and gluons confined inside hadrons undergo a phase transition to a plasma of quarks and gluons and manifested into new phases of QCD, viz. Quark-gluon Plasma (QGP), Color-superconductivity etc. The last three decades of high energy nuclear and particle physics activity has been directed towards the production of this new state of matter through relativistic heavy ion collisions. This has led to experiments at BNL AGS and CERN SPS and to the building of the BNL Relativistic Heavy Ion Collider and the ALICE experiment at the CERN Large Hadron Collider, Geneva. With the reported confirmations of the quark-hadron phase transition at the relativistic heavy ion collision experiments, the first step in the search for QGP, which pervaded the early universe, microseconds after the big bang and which may be present in the core of neutron stars, is complete. QGP is created in the early stage of the collision, it cools rapidly by expanding and emitting various radiation to a hadron gas and then freeze-out, when the particles leave the fireball and reach the detectors. As the lifetime of QGP is very small, a direct detection of QGP in experiments is not possible. In my talk, we will discuss different perspectives of this new matter: how is this new state of matter formed, how can this new matter be diagnosed, how does this phase transition affect big bang nucleosysthesis etc.


About Speaker: Professor in the department of Physics at IIT Roorkee



[127] Topic: Polarimetry of R Aquarii - A Nearby Exploding Star

Speaker: Prof. U. C. Joshi
Affiliation: PRL, Ahamedabad
Date (yyyy-mm-dd): 2015-05-01
Time: 15:30hr
Venue: Auditorium

Abstract: R Aquarii is a nearby unique symbiotic star. The most notable observation is that R Aqr varies in brightness over the course of 387 days, going from an 11th magnitude star to a 6th magnitude star. Apart from this, it show peculiar polarization behaviour. Our earlier study on this source showed strong wavelength dependence of polarization and position angle which also showed strong time dependence. The variation in polarization in U-band was found to be much larger compared to that in longer wavelengths. To understand the long term polarization behaviour, we have been caring out polarimetry on this source since 1995 from Mt Abu observatory, India. In the talk, general characteristics of R Aqr will be discussed along with the focus on the polarization behaviour of this peculiar star.


About Speaker: Prof. U. C. Joshi was a senior professor and chairman of Astronomy and Astrophysics Division of PRL, Ahmedabad.



[126] Topic: Determination of H_0 through monitoring of gravitationally lensed quasars

Speaker: S. Rathna Kumar
Affiliation: Indian Institute of Astrophysics
Date (yyyy-mm-dd): 2015-04-24
Time: 15:30hr
Venue: Auditorium

Abstract: The Hubble constant at the present epoch (H_0) is an important cosmological parameter on which all extragalactic distances depend. Multiple approaches need to be pursued to constrain its value in order to be able to identify and eliminate unknown systematic errors present in any one approach. Strong gravitational lensing offers one method to constrain H_0 free from calibrations associated with standard candles. It is based on (i) measuring the time delay(s) between the multiple images of a cosmologically distant variable source which is strongly lensed by a galaxy or galaxy cluster that lies in close proximity to its line-of-sight and (ii) modelling the mass distribution of the deflector. We have carried out photometric monitoring of a sample of six gravitationally lensed quasars using the 2-m Himalayan Chandra Telescope (HCT) as part of the COSmological MOnitoring of GRAvItational Lenses (COSMOGRAIL) campaign to measure time delays of most known lensed quasars in both hemispheres using a network of medium-size telescopes. I will discuss in detail our results of this campaign, using a newly devised "difference-smoothing" technique to measure time delay and pixellated modelling of the mass distribution of the deflector to constrain the H_0 value. Further, I will also highlight the usefulness of our time delay measurement technique to other AGN monitoring programs, such as reverberation mapping, often used to infer the kinematics of central regions of AGN using 1-2m class telescopes.


About Speaker: Rathna Kumar has applied for a postdoc position in ARIES.



[125] Topic: Photospheric, chromospheric and coronal activities in late type active stars

Speaker: Manoj Kumar Patel
Affiliation: D.D.U. Gorakhpur University
Date (yyyy-mm-dd): 2015-04-29
Time: 15:30hr
Venue: Auditorium

Abstract: I present analyses of optical photometric, spectroscopic and X-ray observations of binary, V1147 Tau and polarimetric observations of other 43 BY Dra type active stars. The continuous photometric monitoring of active stars will leads to study short term as well as long term variations. The long term photometry and analysis of the light curves help to study the different level of activity, the nature of light variability and possible periodicity. The optical spectroscopy revealed that H alpha is present in emission of V1147 Tau, indicating a high levl of chromospheric activity. The polarization values of 43 stars in B, V, R, and I bands decrease towards longer wavelengths, which indicates the possibility of sources of linear polarization as magnetic intensification arise due to stellar spots and as scattering arise due to the thin circumstellar material. The x-ray light curve was found to be rotationally modulated and was anticorrelated with optical light curves observed at quasi-simultaneous epochs. At the end of the talk, I will discuss the research plan of other type active stars during the PDF


About Speaker: Dr. Manoj Kumar Patel has obtained his PhD thesis awarded from D. D. U. Gorakhpur University. He has applied for postdoc position in ARIES.



[124] Topic: Photospheric, chromospheric and coronal activities in late type active stars

Speaker: Manoj Kumar Patel
Affiliation: D.D.U. Gorakhpur University
Date (yyyy-mm-dd): 2015-04-19
Time: 15:30hr
Venue: Auditorium

Abstract: I present analyses of optical photometric, spectroscopic and X-ray observations of binary, V1147 Tau and polarimetric observations of other 43 BY Dra type active stars. The continuous photometric monitoring of active stars will leads to study short term as well as long term variations. The long term photometry and analysis of the light curves help to study the different level of activity, the nature of light variability and possible periodicity. The optical spectroscopy revealed that H alpha is present in emission of V1147 Tau, indicating a high levl of chromospheric activity. The polarization values of 43 stars in B, V, R, and I bands decrease towards longer wavelengths, which indicates the possibility of sources of linear polarization as magnetic intensification arise due to stellar spots and as scattering arise due to the thin circumstellar material. The x-ray light curve was found to be rotationally modulated and was anticorrelated with optical light curves observed at quasi-simultaneous epochs. At the end of the talk, I will discuss the research plan of other type active stars during the PDF


About Speaker: Mr. Manoj Kumar Patel has recently submitted his thesis in D. D. U Gorakhpur University for PhD degree.



[123] Topic: Search for Pulsational Variability in Chemically Peculiar Stars

Speaker: Sowgata Chowdhury
Affiliation: Tezpur Univerity (pass out)
Date (yyyy-mm-dd): 2015-04-22
Time: 15:30hr
Venue: New Auditorium

Abstract: The Nainital-Cape survey is a dedicated ongoing survey programme to search and study the pulsational variability in chemically peculiar (CP) stars to understand their internal structure and evolution. The main aim of this survey is to find new pulsating Ap and Am stars in Northern & Southern hemisphere and set-up a platform to perform their asteroseismic study. The survey was conducted using high-speed photometry. The candidate stars were selected on the basis of Str"omgren photometric indices similar to those of known pulsating CP stars. More than 300 candidate pulsating CP stars were observed for the Nainital-Cape survey, making it one of the longest survey ever in terms of time span and sample size. Here, we announce the discovery of Delta Scuti type pulsations in Am star HD73045. Apart from this positive detection, we present the light curves, frequency spectra and the various astrophysical parameters of the 108 additional CP stars observed since the last reporting. We have also tabulated an up-to-date list of known roAp stars along with their basic physical parameters. We investigated the scintillation noise level by comparing the combined frequency spectra of the sample stars observed from ARIES and Sutherland around the same time period. Our analysis shows that the stability of sky at Sutherland is better than ARIES, hence remains one of the best site for detection of milli-magnitude (mmag) order light variations.


About Speaker: Sowgata is a VSP student working under Dr. Santosh Joshi at ARIES since last six months.



[122] Topic: Stellar Variability and Rotational Activities in the Kepler field.

Speaker: Sowgata Chowdhury
Affiliation: Tezpur University (passout student)
Date (yyyy-mm-dd): 2015-04-17
Time: 15:30hr
Venue: New Auditorium

Abstract: We present the results of time-series photometric analysis of about 15000 stars observed by the Kepler space mission. We measured star-spot rotation periods of 2275 active stars as a function of spectral type and also discuss the distribution of their amplitudes. We examined the period-color relationship for all the Kepler field rotational variables and interestingly found that the same relationship holds true for both early-F and A type stars. This result is not consistent with the very foundation of the PtM relationship. Through visual inspection of the periodograms and the light curves, we identified 16 stars that have previously been mentioned in the literature as red giants with solar-like oscillations. In addition, we found 72 new candidate solar-like oscillators not previously mentioned in the literature. The basic physical parameters such as masses, radii and luminosities of these solar-like oscillators were also derived using asteroseismic relations. We have characterized several non-radial pulsating variables such as delta Scuti, gamma Doradus and hybrid stars and the relationship between two newly constructed observables, Energy and Efficiency have also been studied for the large sample of non-radial pulsators. Our results also support the idea that the present observational instability strip should be extended to accommodate the newly discovered pulsators.


About Speaker: Sowgata Chowdhury was a project student in ARIES from August-2015.



[121] Topic: SN 2013ej - A TYPE IIL SUPERNOVA WITH WEAK SIGNS OF INTERACTION

Speaker: Subhash Bose
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-04-16
Time: 15:30hr
Venue: Auditorium

Abstract: We present optical photometric and spectroscopic observations of supernova 2013ej. It is one of the brightest type II supernovae exploded in a nearby (~ 10 Mpc) galaxy NGC 628. The light curve characteristics are similar to type II SNe, but with a relatively shorter (~85 day) and steeper (~1.7 mag (100 d)^-1 in V) plateau phase. The SN shows a large drop of 2.4 mag in V band brightness during plateau to nebular transition. The absolute ultraviolet (UV) light curves are identical to SN 2012aw, showing a similar UV plateau trend extending up to 85 days. The radioactive 56Ni mass estimated from the tail luminosity is 0.02 M_sun which is significantly lower than typical type IIP SNe. The characteristics of spectral features and evolution of line velocities indicate that SN 2013ej is a type II event. However, light curve characteristics and some spectroscopic features provide strong support in classifying it as a type IIL event. A detailed SYNOW modelling of spectra indicates the presence of some high velocity components in H_alpha and H_beta profiles, implying possible ejecta-CSM interaction. The nebular phase spectrum shows an unusual notch in the H_alpha emission which may indicate bipolar distribution of 56Ni. Modelling of the bolometric light curve yields a progenitor mass of ~14 M_sun and a radius of ~450 R_sun, with a total explosion energy of ~2.3x10^{51} erg.


About Speaker: SRF at ARIES



[120] Topic: Analytical and numerical simulation of shock tube problem

Speaker: Sananda Raychaudhuri
Affiliation: Bose Institute
Date (yyyy-mm-dd): 2015-04-16
Time: 15:30hr
Venue: New Auditorium

Abstract: Numerical simulation has become the essential tool for theoretical astrophysicist to under stand various astrophysical system. In this one month project we have regenerated all the necessary solutions to understand the state of the art, high-resolution shock capturing, upwind simulation codes.


About Speaker: Sananda Raychauduri is a course work student in Bose Institute. She is interested to pursue PhD in theoretical astrophysics, and has spent about a month in ARIES as VSPA.



[119] Topic: Astrophysics in the fast time domain: capabilities and selected results from the Thai 2.4m telescope

Speaker: A. Richichi
Affiliation: National Astronomical Research Institute of Thailand, Chiang Mai, Thailand
Date (yyyy-mm-dd): 2015-04-13
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: Abstract:- I will present the rapid scientific and technological expansion taking place at the National Astronomical Research Institute of Thailand, the leading institution for astronomy in South-East Asia. The NARIT science group includes scientists with a broad range of interests spanning from solar system objects, to exoplanets, to stellar physics and cosmology. Alongside with a several 50 to 70-cm class telescopes, some of which are fully robotic, the flagship facility is the new Thai National 2.4-m Telescope (TNT), equipped with spectrographs and imaging cameras. TNT is open for observations mostly in the dry season (approx. October to May). I will discuss the characteristics of the site and the opportunities for telescope access and collaboration. I will then discuss in particular ULTRASPEC, a visitor instrument built by a Consortium of UK institutes, based on a low-noise, frame-transfer EMCCD with high-quality optics and high-time resolution capabilities extending to few milliseconds: a niche for which no other observatory is similarly equipped in the longitude range of TNT. By using a highly flexible scheme of subarray reading, sampling rates as fast as 400Hz can be achieved. I provide examples of new exciting results in areas such as eclipsing binaries, cataclysmic variables, flickering, exoplanet transits, and occultations by the Moon and other solar system bodies.


About Speaker: He is Senior Researcher at NARIT, Thailand



[118] Topic: Simulation of CO2 transport by a regional model and comparison with observed data

Speaker: Srabanti Ballav
Affiliation: Jadavpur University
Date (yyyy-mm-dd): 2015-04-10
Time: 15:30hr
Venue: New Auditorium

Abstract: The quantification of source-sink distribution of atmospheric CO2 in a finer resolution can become uncertain due to the CO2 transport model-observation data mismatches. In case of the coarse resolution global model, the mismatch occurs mainly due to unresolved sub-grid scale processes, improper representation of the heterogeneity of surface fluxes and model transport behaviour around the measurement site. So far, the high resolution forward transport model simulations of CO2 at hourly to synoptic timescales have attracted considerable interest. Therefore, we have simulated CO2 concentrations as non- reactive trace gas over the Far East Asian region using the regional model WRF-CO2 developed at Jadavpur University, India and RIGC/JAMSTEC, Japan having realistic meteorology as an integral part of the system and has successfully relaxed the limitation in model horizontal resolution. Such a modeling system also accounts for the heterogeneity in the surface fluxes. Using the WRF-CO2 model we have (i) investigated spatio-temporal scale variation of CO2 concentration with observed data, and carried out model inter-comparison with available data from TransCom3 models, (ii) carried out case studies to evaluate performance of the model for synoptic variation of CO2 concentration and meteorology, (iii) evaluated model performance for simulating the vertical profile of CO2 in a tall tower. Results of our study show significant improvement of CO2 transport simulation for the regional models due to increment of horizontal resolution in finer scale. Higher resolution a priori fossil flux produces better concentration than the coarser resolution flux. Temporal variabilities of CO2 at different observation stations are well captured by the model. Particular case studies of CO2 transport during extreme weather conditions have also revealed that the model performs well. Overall, the WRF-CO2 model is found to perform better than global models in terms of CO2 transport. However, the WRF-CO2 model needs to be further evaluated over different regions of the world. Hence, the present work can be extended using recent observational data acquired by the AIRES, Nainital and aircraft measurement of vertical profile over New Delhi by the Japan Airlines CONTRAIL programme with collaboration from JAMSTEC, and other existing ground based and tall tower data in the South Asia region. Although (Kumar and Naja et al. 2012, GMD) have evaluated WRF-Chem for several other chemical species (CO, O3 and NOx), no high resolution chemistry modeling of CO2 transport has been attempted for the south Asia region. Therefore, this project of the WRF-CO2 modelling for the Himalayan region along with central Indian region would be a first time application of a very high resolution CO2 modelling over India. Furthermore, the current work should be extended to understand temporal variations of long-lived CO2 in our geographical locations. The propose project is envisaged to provide the first time high-resolution CO2 dynamic studies over South Asia. Concentration and flux values of CO2 that will be obtained from the model simulation


About Speaker: Srabanti did her doctoral research under the guidance of Prof. Utpal Dey in Jadavpur University. She is post-doctoral applicant in ARIES.



[117] Topic: Structural Studies of Eight Bright Rimmed Clouds in Southern Hemisphere

Speaker: Saurabh Sharma
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-04-07
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: We have presented wide field deep NIR survey of eight regions containing BRCs to study the initial configuration of the YSOs and their nature of interaction with parent molecular clouds. The completeness limit for our observations in K band is ~18 magnitude. For our sample of BRC having distance around 2-3 kpc, we can detect upto sub-solar mass protostars. In addition to mid-infrared images and near-infrared extinction maps, we have identified and classified numerous YSOs, analyzed their spacings, and performed basic spatial distribution measurements and analyses. We identified and classified 100-300 YSOs in different regions with no more than 10-50 expected to be residual contaminators such as broad-line AGNs. Of those, 60 % are classified as IR excess stars, 20% are classified as CTTS, and 15%, 5% are classified as Class II and Class 0 protostars, respectively. We have also presented a purely algorithmic method to isolate local density enhancements in point source distributions from a more diffuse, poorly sampled, and potentially varying density background that uses no smoothing. This method was applied to our survey, extracting eight cluster cores of 10 or more YSO members. Of the identified YSOs, ~60% are members of one of these cores. We have demonstrated that protostars are found in regions of marginally higher surface densities than the more evolved pre-main-sequence stars with disks. The mean of the median spacings of YSOs (regardless of class) in the eight cores isolated here is ~0.06 pc. There suggestion by other investigations (e.g., Teixeira et al. 2006) that Jeans fragmentation is a worthwhile starting point for understanding primordial structure in star-forming regions. In that light, we infer the natal cloud properties from the mean YSO spacing and an assumed temperature of 20K, arriving at properties that are similar to those reported as probable cluster-forming clumps in infrared dark clouds by Rathborne et al. (2006).


About Speaker: Scientist



[116] Topic: Importance of Magnetic Fields in Spontaneous and Triggered Star Forming Regions

Speaker: Archana Soam
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-03-31
Time: 15:30hr
Venue: New Auditorium

Abstract: In my thesis work, I have tried to understand the relative importance of the mag- netic fields in the regions such as starless/prestellar cores, cores with low-mass and sub-stellar mass objects, and the triggered star forming regions. To arrive at a statisti- cally significant conclusion of this study, I want to increase the sample of these regions. A detailed study of magnetic field maps towards cometary globules (CGs) L331 and L323 in the vicinity of L328 is planned. We have already studied the magnetic fields in L328. The above mentioned two objects L331 and L323 are similar to L328. So we need to observe them to understand the magnetic field morphology in the entire region. I also want to investigate the magnetic field variation in the filamentary clouds which is quite a new and interesting project. This will give us an insight into the understanding of the role of magnetic fields in the the cores forming along the filamentary molecular cloud structures. In addition, I would complete the project started to understand the characteristics of the photoionised gas from the two nebulae Sim 129 and Sim 130 in open cluster NGC 1893. The radio observations in 610 and 1300 MHz frequencies have already been conducted using GMRT. This study will help us in understanding the photoionsed flow from the surface of the bright-rimmed cloud (BRCs) in the vicinity of the high mass stars. NGC 1893 is a interesting region containing five O type stars present in the neighborhood of two above mentioned nebulae. The preliminary results obtained by us suggest that the ionized gas is flowing along the magnetic field lines. These results are obtained based onto the 610 MHz observations. More elaborated and detailed results are expected from the 1300 MHz observations.


About Speaker: Archana Soam is a 6th year student in ARIES, who have submitted her thesis recently. She has applied for Post Doc in ARIES.



[115] Topic: General relativistic description of accretion-ejection mechanism around Compact objects

Speaker: Rajiv Kumar
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-03-24
Time: 15:30hr
Venue: New Auditorium

Abstract: We want to understand the black hole accretion process, outflows and jets, and predict its observational properties. In the study of accretion disc the highly non-linear process involves a transport of angular momentum by turbulent viscosity process and dissipation in the disc by various dissipative process. The disc in a full general relativistic regime is a very hard to study analytically. So here firstly, we have study analytically hydrodynamic disc with using pseudo-Newtonian geometry around compact objects then using full general relativistic approach. Our accretion solutions are stationary, axisymmetric without or with turbulent viscosity in the disc around non-rotating black holes. We have developed all type of possible accretion solutions in a self-consistent manner for non-dissipative or dissipative process in the disc. We have mainly focused on shock disc solutions and jets solutions by assuming jets flow geometry around BH with their corresponding disc luminosities. From this study We want to relate the four features of a black hole observations, which are the disc luminosity, Quasi-periodic Oscillations (QPOs), spectral states of the disc and emitted jets from the disc and try to connect all these observed features each other with shocked accretion disc around black holes.


About Speaker: Rajiv is a 6th year student of ARIES who have recently submitted his thesis, and has applied for post-doctoral fellowship in ARIES.



[114] Topic: Radio Studies of the Nearby Disk Galaxies

Speaker: Dr. Alka Mishra
Affiliation: DDU, GU, Gorakhpur (UP)
Date (yyyy-mm-dd): 2015-02-27
Time: 15:30hr
Venue: ARIES Auditoriuum

Abstract: Galaxies reside in different environments ranging from isolated field galaxies to dense group/cluster medium. Properties of galaxies are influenced by their surroundings. We present a multifrequency radio continuum study of seven giant low surface brightness (LSB) galaxies and HI study of four spiral galaxies residing in a group using the Giant Metrewave Radio Telescope. Our sample consists of giant LSB galaxies that show signatures of nuclear activity in their optical spectra. All the galaxies are HI rich. We compare the radio images with the near-ultraviolet (NUV) images from GALEX and near-infrared (NIR) images from 2MASS. The galaxies present a divers ity of relative NUV, NIR and radio emission, supporting anepis odic star formation scenario. Our multiwavlength study of this sample suggests that the environment plays an important role in the evolution of these galaxies.


About Speaker: Dr. Mishra has completed here Ph D from Gorakpur University.She is PDF candidate at ARIES.



[113] Topic: Theoretical and Numerical Investigations of Accretion-Ejection Mechanism

Speaker: Rajiv Kumar
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-02-23
Time: 15:30hr
Venue: New Auditorium

Abstract: The goal of this thesis is to understand the black hole accretion process, outflows and jets, and predict its observational properties. In the study of accretion disc the highly non-linear process involves a transport of angular momentum by turbulent viscosity process and dissipation in the disc by various dissipative process. The disc in a full general relativistic regime is a very hard to study analytically. So here firstly, we have study analytically hydrodynamic disc with using pseudo-Newtonian geometry around compact objects then using full general relativistic approach. Our accretion solutions are stationary, axisymmetric without or with turbulent viscosity in the disc around non-rotating black holes. We have developed all type of possible accretion solutions in a self-consistent manner for non-dissipative or dissipative process in the disc. We have mainly focused on shock disc solutions and jets solutions by assuming jets flow geometry around BH with their corresponding disc luminosities. From this study We want to relate the four features of a black hole observations, which are the disc luminosity, Quasi-periodic Oscillations (QPOs), spectral states of the disc and emitted jets from the disc and try to connect all these observed features each other with shocked accretion disc around black holes.


About Speaker: Rajiv Kumar is a sixth year student of ARIES. He is about to submit his thesis. His supervisor is Dr. Indranil Chattopadhyay



[112] Topic: Investigation of Star Forming Regions and Young Stellar Objects

Speaker: Archana Soam
Affiliation: ARIES
Date (yyyy-mm-dd): 2015-02-24
Time: 15:30hr
Venue: New Auditorium

Abstract: The study of magnetic fields in molecular clouds formed in various environments have enormous potential towards understanding the underlying physics behind the role played by the magnetic fields in the formation of molecular clouds and the subsequent star formation. The closer and isolated molecular clouds provide the fascinating laboratories where the importance of magnetic fields can be explored towards ongoing activities like evolution of the cloud and star formation. This needs a extensive study of magnetic fields on the large scales of these regions. Therefore, in general, the focus of this thesis is to explore the magnetic fields morphology and strength in various environments of molecular clouds to understand the open issue of the role played by magnetic fields in interstellar medium (ISM). The regions where we have mapped the magnetic fields are broadly classified into the categories viz. triggered star forming and spontaneous star forming sites. In triggered star forming regions, we have chosen the multiple bright-rimmed clouds (BRCs) and cometary globules (CGs) associated to some HII regions surrounded by a high mass star in the center. When a massive star forms, it photoionizes the surroundings, forming an HII region which display highly irregular structures such as BRCs. The radiation driven implosion process explains the photoionization induced collapse of a dense, isolated cloud that is illuminated from one side by a source of ionizing radiation. In the presence of magnetic fields, the dynamical evolution of the globule and ionized gas streaming out of the globule surface get modified significantly depending on the strength and the orientation (w.r.t the direction of incoming ionizing radiation) of the magnetic field. These HII regions are selected because of their structural simplicity and proximity to the sun. The advantage of studying multiple BRCs associated with the same HII region is that one can perform a comparative study of the magnetic field morphology at various locations of the HII region w.r.t. the direction of the ionizing radiation from the central source. Magnetic fields in a significant number of BRCs and CGs located in northern hemisphere have not been explored comprehensively. In order to examine the role played by the magnetic fields in the formation and further evolution of structures like BRCs and CGs on the periphery of HII regions, an attempt of mapping the large scale magnetic fields has been made using optical, near-IR (NIR) and submillimeter (submm) polarisation techniques. The observed polarisation is caused by the selective extinction of the light as it passes through the elongated dust grains that are aligned with their minor axis parallel to the local magnetic fields of the cloud. Moreover, our investigations reveal the effects of ionising radiation on the inherent magnetic field structures in these regions. In one part of the thesis, the plane of the sky magnetic fields morphologies in BRCs and CGs associated to HII regions Sh 2-185, Sh 131, Sh 236, Sh 126, Orion and Ophiuchus molecular clouds, are studied. Various orientations of fields lines w.r.t. the incoming high energy radiation from the nearby ionising source have been found. Based on these orientation, the evolution of BRCs and CGs are attempted to be understood by comparing the observational results with the prevailed magnetohydrodynamics (MHD) simulations. Firstly, we categorized the results of observations of the magnetic fields direction in BRCs and CGs as parallel, perpendicular and inclined w.r.t. the incoming ionising radiation. Using these observations and comparison with simulations, the radiation driven implosion (RDI) process has been attempted to be understood in this work. Along with the evolution of globules in context of the magnetic fields, we have also mapped the ionized gas using radio continuum observations towards a open cluster NGC 1893 containing a number of O type stars. The magnetic field structure have been found responsible for the morphology of these clouds. The fields lines are found to be following the ionised gas mapped using the radio observations. It has been widely accepted that the magnetic fields play an important role in the spontaneous star formation process. The influence of magnetic fields in all stages of cloud and star formation is still unclear. In a magnetic field dominated scenario for isolated low-mass star formation, the cores are envisaged to gradually condense out of a magnetically subcritical background cloud, through ambipolar diffusion. To under- stand the evolution of magnetic fields in the cores of different ages (ages determined based onto the chemical evolution), we have studied the magnetic fields in a number of prestellar cores. Magnetic fields morphology in some of the cores harboring very low luminosity objects (VeLLOs) have also been made in this thesis. These studies will help in understanding the standard models of low mass star formation and key role played by the magnetic fields in these processes. In order to understand the disk formation in the low mass stars, we have studied the magnetic field structure and following alignment/misalignment between the mean magnetic field direction and the rotation axis (the outflow axis is presumed to be the rotation axis of the core) in a core with a proto-brown dwarf candidate as a central object. Magnetic field strength have been estimated using the modified Chandrasekhar-Fermi (CF) relation. The magnetic fields direction in general is found to be parallel to the minor axes and aligned with the outflow direction from the central object. These result support the standard models of low mass star formation. This thesis also contains a small catalog containing fainter polarized standard stars available in the fields of already found brighter polarized standard stars described in the literature. These brighter standard stars, when observed with big aperture telescope, get saturated. Hence the fainter standard stars listed in this thesis will solve the issue of the saturation of the stars.


About Speaker: Archana Soam is 6th year student in ARIES, who is about to submit her thesis. Her supervisor is Dr. Maheswar Gopinathan



[111] Topic: First optical and near infrared polarimetry of a molecular cloud forming a proto-brown dwarf candidate

Speaker: Archana Soam
Affiliation: ARIES
Date (yyyy-mm-dd): 2014-12-30
Time: 15:30hr
Venue: Auditorium

Abstract: LDN 328 is cited as an example of a fairly isolated clump contracting to form multiple sub-cores possibly through gravitational fragmentation. In one of these sub-cores, a proto-brown dwarf (L328-IRS) candidate is in the process of formation through the self gravitating contraction, similar to the formation scenario of a low mass normal star. We present results of our optical and near infrared polarisation observations of regions towards LDN 328. This is the first observational attempt to map the magnetic field geometry of a cloud harboring a proto-brown dwarf candidate associated with a sub-parsec scale molecular outflow. On a parsec scale, the magnetic field is found to follow the curved structure of the cloud showing a head-tail morphology. The projected angular offset between the magnetic field and the outflow is found to be around 40 degree. The magnetic field is found to be well ordered over 0.02−0.2 pc scale around L328-IRS. Considering outflow to be the proxy for the rotation axis, the result implies that the rotation axis is tilted by around 40 degree with respect to the local magnetic field (at 0.02 − 0.2 pc scales). The magnetic field strength estimated in the close vicinity of L328-IRS is approx 20 microGauss. Comparing our results with those from the recent simulations, for the estimated strength of the magnetic field, the observed tilt angle (between the magnetic field and rotation axis) alone may not be sufficient to resolve the magnetic breaking problem to facilitate the formation of centrifugally supported disk.


About Speaker: Archana is a Senior Research Fellow at ARIES



[110] Topic: On Characterization of trajectories in Restricted 3-Body problem with Radiation Pressure: Application Binary stellar System

Speaker: Dr. M.K.Das
Affiliation: University of Delhi South Campus
Date (yyyy-mm-dd): 2014-11-24
Time: 15:30hr
Venue: Auditorium

Abstract: Mathematical formulation of the stability of orbits in Restricted 3-Body Problems have been described. In this connection the computation of Poincare section method and wavelet analysis has been described with a view to analyze the nature of orbits in Sun-Jupiter system. Further the extension of the work to include the effect of radiation has been discussed. Such a framework has been used to discuss the stability of orbit in Binary stellar system Kruger-60 and RW-Monocerotis.


About Speaker: Prof. at Institute of Informatics & Communication University of Delhi South Campus



[109] Topic: Strengthening astronomical cooperation between India and South Africa

Speaker: Prof Nithaya Chetty
Affiliation: Deputy CEO: National Research Foundation
Date (yyyy-mm-dd): 2014-11-13
Time: 15:30hr
Venue: Auditorium

Abstract: Since 2012, India and South Africa have been discussing modalities for astronomical cooperation between our two countries. In October 2014, a Concept Note was finalised that sets out to define the areas of cooperation. This talk will give a brief outline of astronomy developments in South Africa, with a view to exploring areas of cooperation.


About Speaker: Deputy CEO: National Research Foundation



[108] Topic: Astronomy at the South African Astronomical Observatory

Speaker: Ted Williams
Affiliation: Director, SAAO
Date (yyyy-mm-dd): 2014-11-13
Time: 16:00hr
Venue: Auditorium

Abstract: The current status of the telescopes and instruments at the SAAO will be discussed, and our plans for future developments. Opportunities for international participation between India and South Africa are abundant, bot for observational programs and instrument development.


About Speaker: Director, SAAO. Professor of Physics and Astronomy, Rutgers University. Honorary Professor, University of Cape Town.



[107] Topic: Aerosol chemistry and acid rain

Speaker: Dr P S P Rao
Affiliation: IITM, Pune
Date (yyyy-mm-dd): 2014-11-17
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: Aerosol chemistry is important in studies related to radiative forcing, air quality, climate change etc. Chemical composition of precipitation reflects the chemical status of the atmosphere. These studies are needed to understand the deposition fluxes, biogeochemical cycles of important nutrients i.e., N and S. The effects of acid rain on forests, soils, lakes and monuments will be presented. The collection and analysis of precipitation, ionic composition of precipitation in different environments will be presented. The non-sea salt components, neutralization factors of various ions will be explained. Source identification of various ions will be presented. Long term trends in precipitation chemistry will be shown. The collection and analyses of aerosols and the aerosols chemistry in different environments will be shown.


About Speaker: Speaker is a Senior Scientist at IITM, Pune



[106] Topic: Seeing what we hear: finding electromagnetic counterparts for gravitational wave sources

Speaker: Varun Bhalerao
Affiliation: DST-INSPIRE Faculty Fellow, IUCAA
Date (yyyy-mm-dd): 2014-11-07
Time: 11:00hr
Venue: ARIES Audotorium

Abstract: Within this decade, a global network of advanced gravitational wave detectors including LIGO-India are expected to detect various gravitational wave sources. These detectors can yield certain parameters of the gravitational wave source, but complementary studies in electromagnetic wavelengths are crucial for a complete astrophysical understanding. In this talk, I will talk about the proposed electromagnetic counterparts of these sources, and the extremely challenging problem of detecting them. I will highlight why India forms a key node in this global effort, and discuss prospects of optical, IR, radio and X-ray follow-up from India.


About Speaker: Varun Bhalerao is a young scientist working at IUCAA Pune.



[105] Topic: Seeing what we hear: finding electromagnetic counterparts for gravitational wave sources

Speaker: Varun Bhalerao
Affiliation: DST-INSPIRE Faculty Fellow
Date (yyyy-mm-dd): 2014-11-07
Time: 11:00hr
Venue: ARIES Audotorium

Abstract: Within this decade, a global network of advanced gravitational wave detectors including LIGO-India are expected to detect various gravitational wave sources. These detectors can yield certain parameters of the gravitational wave source, but complementary studies in electromagnetic wavelengths are crucial for a complete astrophysical understanding. In this talk, I will talk about the proposed electromagnetic counterparts of these sources, and the extremely challenging problem of detecting them. I will highlight why India forms a key node in this global effort, and discuss prospects of optical, IR, radio and X-ray follow-up from India.


About Speaker: Varun Bhalerao is a young scientist working at IUCAA Pune.



[104] Topic: Planet formation in protoplanetary disks: A Spitzer IRS survey of young stars in nearby star forming regions

Speaker: Manoj Puravankara
Affiliation: TIFR
Date (yyyy-mm-dd): 2014-11-07
Time: 15:30hr
Venue: Auditorium

Abstract: Protoplanetary disks are the birth places of planetary systems. Most young stars are surrounded by such planet forming disks. The onset of the processes associated with planet formation significantly alter the radial and vertical structure of the disks, modify the gas and dust content in them, and cause grain growth and crystallisation of the dust in the disks. Observationally, these structural and evolutionary changes are best studied at infrared wavelengths. As part of a large Spitzer Infrared Spectrograph (IRS) survey, we have obtained and analysed mid-infrared (5-40 micron) spectra of several hundred young protoplanetary disks in the nearby star forming regions. I will present the main results of this survey and discuss their implications for our understanding of the early stages of planet formation and the evolution and eventual dissipation of protoplanetary disks.


About Speaker: Manoj is a faculty at TIFR



[103] Topic: Study of supernovae and massive stars and prospects with the 4m International Liquid Mirror Telescope

Speaker: Brajesh Kumar
Affiliation: ARIES, student
Date (yyyy-mm-dd): 2014-10-31
Time: 15:00hr
Venue: New Auditorium

Abstract: Massive stars are the progenitors of the most energetic explosions in the Universe such as core-collapse supernovae (CCSNe) and gamma ray bursts. During their life time they follow various evolutionary phases (e.g. supergiant, luminous blue variable and Wolf-Rayet). They strongly influence their environments through their energetic ionization radiation and powerful stellar winds. Furthermore, the formation of low- and intermediate-mass stars are also being regulated by them. The Carina nebula region, which hosts a large population of massive stars and several young star clusters, provides an ideal target for studying the feedback of massive stars. In this thesis, we investigated a wide field (32 × 31) region located in the west of the Carina nebula and centered on the massive binary WR 22. For our study, we used new optical photometry (UBVRI H_alpha), along with some low resolution spectroscopy, archival near infra-red (2MASS), and X-ray (Chandra, XMM-Newton) data. We estimated several parameters such as reddening, reddening law, etc. and also identified young stellar objects located in the region under study. Among the various types of CCSNe, Type IIb are recognized with their typical observational properties. Some of them show clear indication of double peaks in their light curves. The spectral features of these SNe show a transition between Type II and Type Ib/c events at early and later epochs, respectively. It has been noticed that the occurrence of these events is not common in volume limited surveys. In this thesis we have studied the properties of the light curve and spectral evolution of the Type IIb supernova 2011fu. The observational properties of this object show resemblance to those of SN 1993J with a possible signature of the adiabatic cooling phase. When light passes through the expanding ejecta of the SNe, it retains information about the orientation of the ejected layers. In general, CCSNe exhibit a significant level of polarization during various phases of their evolution at different wavelengths. We have investigated the broad band polarimetric properties of a Type II plateau SN 2012aw and compared it with other well-studied CCSNe of similar kinds. In the framework of the present thesis, we have also contributed to the development of the 4m International Liquid Mirror Telescope (ILMT) project which is a joint collaborative effort among different universities and research institutes in Belgium, India, Canada and Poland. We performed various experiments including the spin casting of the primary mirror, optical quality tests of the mercury surface, mylar film experiments, etc. The possible scientific capabilities and future contributions of this telescope are also discussed. We propose our plans to identify the transients (specially supernovae) with the ILMT and their further follow-up scheme. The installation of the ILMT will start very soon at the Devasthal observatory, ARIES Nainital, India.


About Speaker: Mr. Brajesh Kumar has completed his full tenure of seven years as ARIES PhD student. This talk is being organized as his thesis pre-submission talk.



[102] Topic: Investigation of the stellar variability and Rotational Activities in Kepler Field

Speaker: Mr. SOWGATA CHOWDHURY
Affiliation: Tejpur University
Date (yyyy-mm-dd): 2014-10-31
Time: 12:15hr
Venue: Auditorium

Abstract: In this talk, I present the results on the time-series photometric analysis of approximately 15000 stars observed by Kepler space mission. We announce some discoveries such as solar-like oscillations in 83 red giants, 52 eclipsing binary systems etc. We have estimated the rotation periods of 2948 active stars and discuss the distribution of their frequencies and amplitudes. Interestingly, we have found star-spots in several A-type stars and observed that the number of A-type stars with starspots increases with decreasing amplitude. Using asteroseismic technique we have derived the basic astrophysical parameters such as masses, radii and luminosities of the 113 red giants. We have also found many new flares on late type stars, non-radial pulsating variables such as Delta Sct, Gamma Dor stars etc..


About Speaker: Mr. Sowgata Chowdhury is a project student working with Dr. Santosh Joshi since last three months. He has requested extension for next three months to complete his project.



[101] Topic: Luminous SN 2012aa : Implication of shock interaction on the observed properties

Speaker: Rupak Roy
Affiliation: Oskar Klein Centre, Sweden
Date (yyyy-mm-dd): 2014-10-30
Time: 15:30hr
Venue: Auditorium

Abstract: Recent development on supernova research has confirmed that there is a distinct class of events which are more luminous than canonical core-collapse supernovae (CCSNe). Typically they show a broad peak (~ -21 mag) with a shallower decline rate than normal events. SN 2012aa, which was discovered in a relatively distant (redshiftz ≈ 0.08) host galaxy on 29.6 January 2012 UT by the Lick Observatory Supernova Search (LOSS), has similar characteristics. The event was also detected by the Catalina Real-Time Transient Survey (CRTS) during its rising phase, with peak apparent unfiltered magnitude ~ 18. From optical spectra it was characterized as a Type Ic SN, although photometrically it is quite distinct from canonical Type Ic events. The photometric and spectroscopic follow-up over a span of 100 days clearly shows the signature of interaction of the SN-shock with the circumsteller medium (CSM). The post-maximum decay rate of this event is roughly 0.012 mag/day. This is much lower than that of normal stripped-envelope CCSNe (~0.06 mag/day) and comparable to the decay rate of  superluminous events like CSS100217 and SN 2007bi. However beyond 60 days, the decay rate becomes comparable with that of radioactive 56^Co. Here, I shall present the optical photometric and spectroscopic follow-up observations of this event, along with detailed analysis of the light curve and spectra, which demonstrate the interaction of SN-shock with the CSM.


About Speaker: Postdoc at Oskar Klein Centre, Sweden http://okc.albanova.se/



[100] Topic: Persistent Organic Pollutants – A Global issue

Speaker: Dr Ishwar Chand
Affiliation: Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, Chi
Date (yyyy-mm-dd): 2014-10-13
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: Persistent Organic Pollutants are organic chemical substances those persist in the environment and pose a risk of adverse effects to human health and environment. These are global pollutant, due to their longer life, and migrate over long distances. Most POPs generated in one country can and do affect people and wildlife far from where they are used and released. They persist for long periods of time in the environment and can accumulate and pass from one species to the next through the food chain. Considering their global impact, multilateral environmental agreement (United Nations treaty) is signed in Stockholm, Sweden, in May 2001 to reduce or eliminate the production, use, and/or release of 12 key POPs. More details on POPs will discusses during the presentation.


About Speaker: Speaker is TWAS-CAS Postdoctoral Fellow at , Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China



[99] Topic: Accretion processes on Black Holes: A review

Speaker: Sandip Chakrabarti
Affiliation: S.N. Bose National Center for Basic Sciences
Date (yyyy-mm-dd): 2014-10-17
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: We discuss how incomplete the models of thin, thick, slim or ADAF disks are. We show that all the corrected solutions of the above models can be recovered from transonic accretion disks which are advective in nature by definition. We present viscous transonic solutions with radiative transfer, and numerical simulations resutls to show their stability. Finally, we show results of data fitting using the generalized transonic flow solutions.


About Speaker: Sandip is well-known physicist and Senior Professor at S.N. Bose National Center for Basic Sciences.



[98] Topic: X-ray observing technique

Speaker: Jeewan C. Pandey
Affiliation: Scientist D at ARIES
Date (yyyy-mm-dd): 2014-10-31
Time: 17:30hr
Venue: New Auditorium

Abstract: In this talk, I will highlight basic techniques of X-ray observations used in present era observatory like XMM-Newton and Chandra. Both telescopes provide the low as well as high resolution spectroscopy and photometry. Towards the end of talk I would like to summarize the important results obtained by these telescopes.


About Speaker: The speaker is Scientist at ARIES



[97] Topic: Thermal Radiation

Speaker: Dr. Arun Awasthi
Affiliation: Post Doc fellow at ARIES
Date (yyyy-mm-dd): 2014-09-12
Time: 19:00hr
Venue: New Auditorium

Abstract: Thermal radiation is produced by particles with a Maxwellian distribution function, which are found in collisional plasmas, such as in the solar chromosphere or in flare loops. The main type of thermal radiation is free-free (bremsstrahlung), which can be observed in hard X-rays as well as in microwaves. The equilibrium between absorption and emission processes is expressed with the radiative transfer equation. A thermal equilibrium is realized in a black body according to Kirchhoff’s law. In a plasma, where electrons and ions are free (above the ionization temperature), free electrons become scattered in the Coulomb field of ambient free ions, which produces the so-called free-free bremsstrahlung emission. In a thermal plasma there are abundant collisions between free electrons and free ions. There are a large number of atomic processes that are possible in a collisional plasma, including various ionization and recombination processes. A local thermodynamic and ionization equilibrium defines the number of bound-bound transitions in a plasma, expressed by the Saha equation.


About Speaker: The speaker is currently a post doc. fellow at ARIES



[96] Topic: Multi-wavelength diagnostics of energy transportation and triggering of X1.2 class solar Flare observed on May 15, 2013

Speaker: Aabha Monga
Affiliation: ARIES
Date (yyyy-mm-dd): 2014-09-09
Time: 10:00hr
Venue: New Auditorium

Abstract: We study the energy build-up and trigger processes responsible for a X1.2 class solar flare that occurred in NOAA AR 11748, having βγδ magnetic complexity observed on May15, 2013. The flare was well observed by ground based (Hα ARIES, Nainital) and space borne (SDO, HMI). The flare shows two ribbons structures. Morphology of the flare ribbons shows that the brightening propagates along the southern ribbon. We have noticed several Hα kernels that shows different spatially and temporally evolutionary behavior. On the contrary, we do not find filament associated with this event. Therefore, to explore the driver of instability leading to this highly energetic flare, we study the morphological evolution of the active region using SDO and Hα data. We also study the evolution of photospheric magnetic field parameters from SDO/HMI magnetograms in conjunction to the E/UV emission. From AIA EUV images, we note sets of coronal loops over the active region, which show upward motion with the time. We explicitly note mass ejection and disruption of coronal loops. From this study, we infer that this flare occurred in the lower corona as the coronal loops moved upward which gives the signature of magnetic reconnection beneath the uprising loops.


About Speaker: Abha has entered the 3rd year as ARIES PhD student. This is her JRF to SRF talk.



[95] Topic: General theory of spherical accretion and Parker winds

Speaker: Mukesh Kumar Vyas
Affiliation: Research Scholar, ARIES
Date (yyyy-mm-dd): 2014-09-05
Time: 19:00hr
Venue: New Auditorium

Abstract: The talk deals with the physical and mathematical interpretation of two aspects of hydrodynamic model of astrophysical objects, spherical accretion (Bondi 1952) and outflows (Parker 1958). The talk touches approximately most of the branches of astronomy and astrophysics, where it is widely applicable. Various astrophysical implications will also be discussed.


About Speaker: The speaker is IInd year student, PhD program at ARIES



[94] Topic: Astrometric and Photometric Studies of Star Clusters

Speaker: Devesh PathSaria
Affiliation: ARIES
Date (yyyy-mm-dd): 2014-09-04
Time: 15:30hr
Venue: New Auditorium

Abstract: Astrometry of stars in star clusters was least explored for many decades in the last century until the advent of CCD. Photographic plates were yielding a poor number of stars in star-rich clusters with the epoch gap of many decades. With wide field CCD data, it is now possible to probe much fainter regions of stellar clusters to achieve precise proper motions with the epoch gap now being reduced to a few years. Applications of such studies are numerous. These include, deriving precise fundamental parameters of star clusters using most probable cluster members based on membership probabilities values calculated using proper motions, finding absolute proper motions and using them to understand space motion of a star cluster in the Galaxy. To get precise positions and proper motions for large number of stars in the cluster regions, we need wide and high quality images taken at good (~1 arcsec) seeing conditions. For this purpose, we have selected the two epoch data set taken with wide-field imager mounted on 2.2-m telescope installed at La Silla, Chile. We have used the exclusive software developed by Anderson et al. (2006) to calculate proper motions of the stars in the clusters regions. One of the main aim of our work was to provide proper motions and membership probabilities in the region of globular cluster NGC 6809 (M55) in the wider region and fainter magnitudes than previous studies of the cluster. We have derived precise proper motions and astrometric membership probabilities for 12600 stars down to V ~20 mag in 26X22 area. The measurement error in proper motions for the stars of V < 17 mag is 2.0 mas/yr, gradually increasing up to ~ 3 mas/yr at V = 20 mag. We also provide the membership probabilities for the published variables and X-ray sources in the cluster region. All the known SX Phe and RR Lyrae found in our data are most probable cluster members based on our membership catalogue. Open cluster NGC 3766 was studied for the first time with the aim of astrometry. Proper motions and membership of ~2500 stars were estimated and the membership catalogue was used to determine age and mass function slop of the cluster using stars with membership probability >70%. Mass segregation was observed for NGC 3766 and the cluster was found to be dynamically relaxed. To understand the space motion of the globular cluster NGC 6121 (M4), we used Southern Proper Motion (SPM) catalogue in combination with 2MASS catalogue to determine space velocity components of the cluster. The cluster was found to be having a disk-like kinematics. In addition to this, we did time series analysis of the globular cluster NGC 4590 (M68) using the CCD data taken with 104-cm Sampurnand telescope and searched variable stars in its area. We found 40 known and 9 new probable variable stars for which we present phased light curves and periods. In the present talk, I will also state my future research plans.


About Speaker: Devesh has completed six years as PhD student in ARIES. Recently submitted his thesis in Raipur University. This is his post doc evaluation talk.



[93] Topic: X-ray flare on 47 Cas

Speaker: Subhajeet Karmakar
Affiliation: ARIES, Nainital
Date (yyyy-mm-dd): 2014-09-09
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: Using XMM-Newton observation, we investigate properties of a flare from very active and poorly known star 47 Cas B. The luminosity at peak of the flare was found to be 4.77×10^30 erg/s, which is ~2 times more than that from a quiescent state. The quiescent state corona of 47 Cas was represented by two temperature plasma: 3.7 and 11.0 MK. The time-resolved X-ray spectroscopy of the flare showed a variable nature of temperature, emission measure and abundances. The maximum temperature during the flare was found to be 72.8 MK. We inferred the size of a flaring loop using hydrodynamic loop model and the length was found to be of 3.3 × 10^10 cm. Using the RGS spectra, density during the flare was found to be 4.0 × 10^10 cm^(-3). The loop scaling laws were also applied in deriving physical parameters of the flaring plasma.


About Speaker: SRF at ARIES



[92] Topic: Models of disk and jet variability in AGN

Speaker: Dr. Prashanth Mohan
Affiliation: IIA, Bangalore
Date (yyyy-mm-dd): 2014-07-31
Time: 15:30hr
Venue: Auditorium

Abstract: We address optical/UV and X-ray variability attributable to orbital signatures from an emitting blob on the accretion disk or in the relativistic jet. Disk based signatures include the quasi-periodic oscillations (QPOs) and its quality factor, and a break frequency in the power spectral density (PSD) shape of the light curve which are used to constrain black hole mass, spin and the emission region size. A general relativistic (GR) model of jet variability due to an orbiting blob in helical motion along a funnel (or cone) shaped magnetic surface anchored to the accretion disk is then presented. Simulated light curves include Doppler and gravitational shifts, aberration, light bending and time delay. We find an increased amplitude (~ 12 %); beaming and a systematic phase shift in the light curve compared to that from an earlier special relativistic model. These results strongly justify the use of a realistic magnetic surface geometry and a fully relativistic calculation. These models are applicable to the study of disk and jet variability in radio, optical and X-ray emission from sources including AGN, X-ray binaries, accreting neutron stars and supermassive binary black holes.


About Speaker: Dr. Prashanth Mohan is a Post Doctoral Researcher of IIA, Bangalore.



[91] Topic: MULTI-WAVELENGTH STUDIES OF STAR FORMING REGIONS

Speaker: Ramkesh Yadav
Affiliation: ARIES
Date (yyyy-mm-dd): 2014-07-30
Time: 15:00hr
Venue: New Auditorium

Abstract: Star formation in extreme environments such as HII regions is always challenging and can be significantly different from that in quiet environments. HII regions are generally associated with OB stars, which usually form in clustered mode and have profound effect on the parental molecular cloud. The observations of star forming regions can be used to address several questions regarding star formation such as; what are the observational properties of different phases of star formation? How star formation proceeds within a molecular cloud? Whether the star formation is a coeval process? If not then which star forms first? Whether with the formation of massive star(s) in the region, star formation ceases or alternatively trigger(s) new generation of stars through various processes. Therefore, HII regions containing massive fragments or protostars are ideal targets to study different phases of star formation. Which mechanism (spontaneous or triggered) is dominant in a region, is necessary and vital to understand the star formation process within a complex. In this thesis we have tried to answer a few of the such interesting questions. With the advent of new data from deep optical, near-infrared, mid-infrared and X-ray surveys, a considerable interest has been evolved to study low mass young stellar objects (YSOs) as well as to study the evolution of circumstellar disks around the YSOs associated with young star clusters. Several X-ray studies of low-mass PMS stars have been carried out which revealed very strong X-ray activity. The influence of a circumstellar disk, and particularly the influence of accretion on X-ray activity has been of special interest. X-ray studies of PMS stars in star-forming regions have yielded contradictory results. Hence we have re-analyze the X-ray properties of Class II and Class III sources and the relation between rotation and X-ray activity in TTSs using the sample of the YSOs identified by Pandey et al. (2013) and the rotation period of the YSOs determined by Lata et al. (2012), Lata et al. (2014) for the YSOs in the field of young open cluster NGC 1893.


About Speaker: Ramkesh Yadav is seventh year student in ARIES, completing his PhD under the guidance of Dr. A. K. Pandey.



[90] Topic: Multi-band Optical/NIR Variability Studies of the Blazar 3C 454.3

Speaker: Ms. Aditi Agarwal
Affiliation: ARIES
Date (yyyy-mm-dd): 2014-07-28
Time: 11:30hr
Venue: Auditorium

Abstract: We have carried out photometric monitoring of the bright flat spectrum radio quasar 3C 454.3, which has exhibited remarkably high activity and pronounced variability at all wavelengths since 2001, to search for optical variability on a wide range of timescales. CCD magnitudes in B, V, R and I pass-bands were determined from 63 optical observations made during 2011 – 2014, with an average length of ∼ 4 h each, at seven optical telescopes: four in Bulgaria, one in Greece, and two in India. We measured multiband optical flux and color variations on diverse timescales. Discrete correlation functions were computed among B, V, R, and I observations, to search for any time delays. We found weak correlations in some cases with no significant time lags. The structure function method was used to estimate any characteristic time-scales of variability. We also investigated the spectral energy distribution of 3C 454.3 using B, V, R, I, J and K pass-band data. We found that the source almost always follows a bluer-when-brighter trend. We discuss possible physical causes of the observed spectral variability.


About Speaker: Aditi is 2nd year Ph.D. student in ARIES.



[89] Topic: Astrometric and Photometric Studies of Star Clusters

Speaker: Devesh Path Saria
Affiliation: ARIES
Date (yyyy-mm-dd): 2014-07-21
Time: 15:00hr
Venue: New Auditorium

Abstract: Astrometry of stars in star clusters was not much explored for many decades in the last century until the advent of CCD. Photographic plates were yielding a poor number of stars in star-rich clusters with the epoch gap of many decades. With wide field CCD data, it is now possible to probe much fainter regions of stellar clusters to achieve precise proper motions with the epoch gap now being reduced to a few years. Applications of such studies are numerous. These include, deriving precise fundamental parameters of star clusters using most probable cluster members based on membership probabilities values calculated using proper motions, finding absolute proper motions and using them to understand space motion of a star cluster in the Galaxy. To get precise positions and proper motions for large number of stars in the cluster regions, we need wide and high quality images taken at good (~1 arcsec) seeing conditions. For this purpose, we have selected the two epoch data set taken with wide-field imager mounted on 2.2-m telescope installed at La Silla, Chile. We have used the exclusive software developed by Anderson et al. (2006) to calculate proper motions of the stars in the clusters regions. One of the main aim of the present study is to provide proper motions and membership probabilities in the region of globular cluster NGC 6809 (M55) in the wider region and fainter magnitudes than previous studies of the cluster. We have derived precise proper motions and astrometric membership probabilities for 12600 stars down to V ∼ 20 mag in 26 × 22 area. The measurement error in proper motions for the stars of V ∼ 17 mag is 2.0 mas/yr, gradually increasing up to ∼3 mas/yr at V = 20 mag. We also provide the membership probability for the published variables and X-ray sources in the cluster region. All the known SX Phe and RR Lyrae found in our data are most probable cluster members based on our membership catalogue. Open cluster NGC 3766 was studied for the first time with the aim of astrometry. Proper motions and membership of ~2500 stars were estimated and the membership catalogue was used to determine reddening, distance, age and mass function slop of the cluster using stars with membership probability >70%. Mass segregation was observed for NGC 3766 and the cluster was found to be dynamically relaxed. To understand the space motion of the globular cluster NGC 6121 (M4), we used Southern Proper Motion (SPM) catalogue in combination with 2MASS catalogue to determine space velocity components of the cluster. The cluster was found to be having a disk-like kinematics. In addition to this, we did time series analysis of the globular cluster NGC 4590 (M68) using the CCD data taken with 104-cm Sampurnand telescope and searched variable stars in its area. The search prospered with the detection of 40 known and 9 new probable variable stars for which we present phased light curves and periods. To conclude, astrometry has entered an all new era which is going to see a rather fast boost with the GAIA data coming up in the coming years.


About Speaker: Sixth year PhD student, under the guidance of Dr. Ramakant Singh. This is his thesis pre-submission talk in ARIES.



[88] Topic: Study of surface ozone, oxides of nitrogen, carbon monoxide, and methane at a site in the Indo Gangetic Plain region

Speaker: ADWAIT SHUKLA
Affiliation: INDIAN SCHOOL OF MINES, DHANBAD.
Date (yyyy-mm-dd): 2014-07-11
Time: 14:00hr
Venue: Seminar Hall

Abstract: Observations of surface ozone, CO, NOx, CH4 and NMHCs were made at a semi urban site (Pantnagar) in the Indo-Gangetic plain region. Ozone diurnal variations are characterized by daytime photochemical buildup. Changes in ozone show a systematic increase from January 2014 to June 2014. Diurnal patterns in CO, NOx and THC also follow the characteristics of somewhat polluted site. Daily average values in CO, NOx, and THC follow a reverse trend when compared with that in ozone. Based on the above study it is concluded that - Oxidation of CO and THC in the troposphere results in the production of Ozone. So, emissions of CO and THC must be reduced so as to deal with the surface air pollution problem. In this process NOx plays a very critical role. It is also suggested to carry out a high resolution model study for this region to get better information on the different tropospheric processes occurring in this region.


About Speaker: He is Project Student under Academy Program



[87] Topic: The progress in detection of p-mode spectra of roAp stars: Alpha Circini and Gamma Equulei

Speaker: Dr. David Mkrtichian
Affiliation: National Astronomical Research Institute of Thailand (NARIT) 191 Siriphanich Bld
Date (yyyy-mm-dd): 2014-07-08
Time: 15:30hr
Venue: Auditorium

Abstract: I will give the review on the spectroscopic methods for search for rapid oscillations in magnetic chemically-peculiar stars and present our recent results. For the roAp star Gamma Equulei we discovered 4 new p-modes. These frequencies, in concert with previously known, exibits well defined 62.8 $muHz general frequency spacing in the oscillation spectrum and in echelle-diagram. We concluded, that consecutive overtones of even and odd modes are excited in Gamma Equulei. We found the increase of pulsation amplitude from the photosphere to upper layers and existence transition layer at superficial layer at the atmosphere above which the amplitude of pulsations is decreasing. I will present a discovery of a rich, sub-meter-per-second amplitude p-mode spectrum of roAp star Alp Cir that is based on the HARPS precise radial velocity time-series. Discovered spectrum consist of 36 oscillation modes in the interval of 2173-2641 $mu$Hz and ranging in amplitude from 46 m/s to 56 cm/s. The density of frequencies and their spacings in the spectrum indicates about first detection of excited high-degree (l>3) modes in a spectrum of a roAp star. These discoveries established a new detection limits in the asteroseismology of roAp stars and shows the need for updates in theory and pulsation models of magnetic stars.


About Speaker: Dr. Mkrtichian is senior researcher at NARIT, Thailand



[86] Topic: Probing Central Engine and Environments of Active Galactic Nuclei

Speaker: Ravi Joshi
Affiliation: ARIES
Date (yyyy-mm-dd): 2014-07-04
Time: 15:30hr
Venue: New Auditorium

Abstract: Owing to the high luminosity, quasars can be seen up to the very large distances, as a result their continuum and emission lines studies provides a unique tool to understand the driving parameters of central engine and the protogalaxy environment; and the absorption lines seen in their spectra give an important clue about the AGN feedback processes and the evolution of intergalactic medium, both of these features has been explored here in this thesis. The thesis probe the nature of microvariability properties of broad absorption line quasars (BALQSOs), using both radio-loud and radio-quiet subtypes. It first aim to answer the observed high fraction of variability duty cycle (similar to the blazars) for BAL quasars subclass, which are primarily believed to be radio-quiet in nature. Enlarging the sample of radio-quiet BALQSO by a factor of three, we have shown, for the first time, that only ∼16 per cent of BALQSOs show continuum variability. In a similar study, the extremely radio-loud BALQSOs have shown a similar duty cycle to that of their radio-quiet counterparts, resulting in supporting the models where the outflows, causing the broad absorption lines, may arise from the large variety of viewing angles from the jet axis or perhaps being closer to the disc plane. In a search for an elusive radio-quite counterparts of blazars, the newly discovered AGN class of weak-emission line quasars is found to be the potential candidate. Furthermore, we explore the hypothesis that, whether a weak jet component in radio-quiet AGNs is responsible for the origin of rapid small-scale optical variations or not? Using a sample of 83 radio-quiet quasars whose members has been studied for continuum variability, we have ruled out the weak jet component model in radio-quiet quasars. To probe the quasar environments, the thesis uses both the associated and intervening low ionization MgII absorption lines seen in AGN spectra. In the context the recent evidence of excess (factor ~2) number density, dN/dz, of MgII absorption systems towards blazars over the value known for normal quasars, which has questioned the canonical view of intervening and associated absorption systems, we explore towards large sample of core-dominated and lobe-dominated quasars. One of our main result was that the associated absorbers can be seen even up to mildly relativistic speeds, i.e., several times more than the canonical limit of 5000 km/s adopted in the literature for associated absorbers. The dependence of magnetic filed on the presence and/or absence of the intervening absorbers at cosmic distances along quasar sightlines having polarized light has also been explored. This study has revealed a large contribution of the intervening absorber to the enhancement of residual rotation measure at around 21cm wavelength. Finally, to understand the key question of BALQSOs being overall X-ray weak (i.e., either intrinsic or absorbed), we have explored the CIV absorption line variability to probe the physical conditions near the central engine of a very rare class of X-ray-bright BALQSOs. We found a kinematic shift and strength variability of the CIV BAL trough resulted in a largest kinematic shifts, exceeding by factor of about six as compared to the highest deceleration known till date.


About Speaker: Ravi Joshi is sixth year student of ARIES, working under the guidance of Dr. Hum Chand. This is his thesis pre-submission talk in ARIES.



[85] Topic: The oEA stars

Speaker: Dr. David Mkrtichian
Affiliation: National Astronomical Research Institute of Thailand (NARIT) 191 Siriphanich Bld
Date (yyyy-mm-dd): 2014-07-01
Time: 15:30hr
Venue: Auditorium

Abstract: I will present the review on results of studies of a new class of pulsating mass-accreting stars in the semi-detached Algol-type systems. I will discuss the advantages for studies of oEA stars for asteroseismology, the problem of non-radial mode identification and will show the typical peculiarities of this class of variables based on results of 14 years of photometric and spectroscopic monitoring of selected oEA systems.


About Speaker: Dr. Mkrtichian is senior researcher at NARIT.



[84] Topic: Low energy dispersion relations from Dimension-five Scalar Photon mixing operators and their possible imprint on radiations from compact objects.

Speaker: Dr. Avijit Ganguly
Affiliation: Department Of Physics, MMV
Date (yyyy-mm-dd): 2014-06-26
Time: 15:30hr
Venue: ARIES auditorium

Abstract: Identification and search for possible dark matter candidates has occupied an important place in modern day cosmology. Axion, Chameleon, Dilaton, Kaluza Klien excitations, are some of the possible candidates of ark matter. These particles are generally of two types (i) pseudo-scalar (ii) scalar. Except for the pseudo-scalar particle Axion ( postulated to solve the strong CP problem), others originate in unified theories of gravity with U(1) gauge theory. However, in-spite of their difference in origin; the operator structure of their interaction term with photon, have mass dimension equal to five. Which is makes the theory perturbatively non renormalizable. This aesthetically unpleasant interaction ,introduces two additional phenomena, (a) it makes the vacuum optically active (b) In the presence of a back ground magnetic field, some of the physical modes of the theory show signs of instability---in some energy interval. Some of these and related issues will be discussed in this talk. Possible ways to identify the imprints of such interactions from astrophysical objects will also be discussed.


About Speaker: He is professor in Banaras Hindu University



[83] Topic: Charged Particle accelerator for Research and Applications

Speaker: Prof. R. K. Bhandari
Affiliation: Raja Ramanna Fellow, IUAC Delhi
Date (yyyy-mm-dd): 2014-06-24
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: Cyclotron is used for advance Nuclear Physics Research by Scientist from R & D institute and University. This talk will overview the importance of Charged Particle accelerator for Research and other Applications.


About Speaker: Prof. Bhandari, is an Accelerator scientist, worked with the department of atomic Energy for about 40 yr at Variable Energy Cyclotron center (VEC), Kolkatta. He has retired in June 2012 as Director of the VEC, Kolkatta. At preset his interest is to make use of Cyclotron for advance Nuclear Physics Research as well as for other applications.



[82] Topic: Study of Transients and Waves in the Solar Atmosphere

Speaker: Pradeep Kayshap
Affiliation: ARIES, 4th year student
Date (yyyy-mm-dd): 2014-06-19
Time: 15:30hr
Venue: New Auditorium

Abstract: Transients and magnetohydrodynamic (MHD) waves are ubiquitous in the solar atmosphere, which play a crucial role in the energy and mass transport. Therefore, understanding of the drivers and physical properties of these phenomena is at the forefront of solar physics research. Under the framework of the topic of my Ph.D. thesis, some transients at diverse spatio-temporal scales, as well as the role of MHD waves and pulses in these transients have been investigated. In the first chapter, I present an updated overview, reviewing comprehensively the physics and recent developments in various transients and MHD waves, and finally outline the plan of my various thesis chapters. In the second chapter, I report the estimated plasma properties of an active region surge using SDO/AIA, HMI observations, and conclude by our model that thermal pulse in the lower solar atmosphere can trigger the observed surge. The third chapter describes that the internal reconnection in the kinked small-scale magnetic fluxtube evolving at the polar cap of the Sun, triggers a macrospicule and associated coronal jet. The stringent 2-D MHD model depicts that the small-scale reconnection originates a velocity pulse, which steepens in the polar corona and generates the observed macrospicule and jet like plasma perturbations. Another case study of Alfven wave driven polar coronal jet, using Hinode/EIS spectral observations, is also presented in the same chapter. It is found that the reconnection in the 2-D vertical current sheet in polar corona triggers Alfven waves and related vertical plasma flows, which constitute the observed jet-like motion. In the fourth chapter, I investigate the source regions of the plasma flows and signature of the Alfvén waves in the quiet-Sun (QS) and coronal holes (CH) using the spectroscopic observations of Hinode/EIS, which have significant physical implications on the localized coronal heating and mass transport to the nascent fast solar wind. I have finally reported the first observational evidence of sausage-pinch magnetohydrodynamic (MHD) instability in a large-scale eruptive prominence tube in the fifth chapter, and discuss its physical significance in the solar coronal eruptions and magnetized plasma. In conclusion, the original research works as described in various chapters of my thesis, shed new light to the physical properties and drivers (MHD waves, pulses, instabilities) of the solar transients at diverse spatio-temporal scales.


About Speaker: Pradeep is fourth year student of ARIES, who did his PhD research under the guidance of Dr. A. K. Srivastava who was a faculty of ARIES till December 2013.



[81] Topic: Observing multiply imaged quasars with the 4m International Liquid Mirror Telescope

Speaker: Prof. Jean Surdej
Affiliation: Institute of Astrophysics and Geophysics, Liège University, Belgium
Date (yyyy-mm-dd): 2014-06-11
Time: 15:30hr
Venue: Auditorium

Abstract: I shall first remind the basic properties of gravitational lens systems and how these can be used to derive interesting astrophysical and cosmological parameters. I shall specially address the case of symmetric gravitational lens systems for which such parameters can be derived irrespective of the assumed lens model. I shall then describe the 4m International Liquid Mirror Telescope project and explain how this telescope, to be be soon erected on the ARIES site in Devasthal (Uttarakhand), will be used to detect and monitor approximately 50 cases of multiply imaged quasars.


About Speaker: Prof. Jean Surdej is professor at University of Liège, Belgium.



[80] Topic: Seasonal inhomogeneity in cloud precursors over Gangetic Himalayan region during GVAX campaign

Speaker: Dr U C Dumka
Affiliation: ARIES
Date (yyyy-mm-dd): 2014-06-10
Time: 15:30hr
Venue: Auditorium

Abstract: Atmospheric aerosols act as key elements of cloud microphysics, hydrological cycle and climate by serving as cloud condensation nuclei (CCN). The present work analyses simultaneous measurements of number concentration of CCN (NCCN) and condensation nuclei (NCN) obtained at Nainital, in the Gangetic-Himalayan (GH) region, during the frameworks of Ganges Valley Aerosol Experiment (GVAX), June, 2011 to March, 2012.


About Speaker: Scientist at ARIES



[79] Topic: Scattering and absorption properties of near-surface aerosol over Gangetic-Himalayan region, India using Atmospheric Radiation Measurement Mobile Facility

Speaker: Dr U C Dumka
Affiliation: ARIES
Date (yyyy-mm-dd): 2014-06-06
Time: 15:30hr
Venue: Auditorium

Abstract: Knowledge of light scattering and absorption properties of atmospheric aerosols is of vital importance in evaluating their types, sources and estimating the radiative forcing of climate. This is of particular interest over the Gangetic-Himalayan (GH) region due to large aerosol loading over the plains and the uplift over the Himalayan range causing serious effects on atmospheric heating, glaciology and monsoon circulation. In this respect, Ganges Valley Aerosol Experiment (GVAX) was initiated over the region aiming to examine the aerosol properties, source regions, uplift mechanisms and aerosol-cloud interactions. Present study examine the temporal (monthly, seasonal) evolution of scattering and absorption coefficients, their wavelength dependence, role of the Indo-Gangetic plains (IGP), boundary-layer dynamics and long-range transport in the aerosol uplift over the Himalayan foothills.


About Speaker: Scientist at ARIES



[78] Topic: Polarimetry: a powerful diagnostic tool in astronomy

Speaker: Prof. U. C. joshi
Affiliation: PRL, Ahmedabad
Date (yyyy-mm-dd): 2014-06-03
Time: 15:30hr
Venue: Auditorium

Abstract: Every astronomical object is polarized to some degree and therefore, astronomical polarimetry gives more information then imaging/ spectroscopy alone. Polarization ie the vector properties of (scattered) starlight depend on the physical circumstances of the location where the light originate. Many properties of scattering dust clouds can be obtained through polarimetry: the sizes, shapes and chemical composition of the scatterers. Even the content, structure and stratification of the atmosphere of some of the stars, planets or exoplanets can, in principle, be characterised without optically resolving them. Another important and unique capability of polarimetry is the measurement of magnetic fields. Astronomical polarimetry has, therefore, unique capability. In this talk basics of polarimetry along with polarization studies in PRL on a few different kind of sources will be discussed.


About Speaker: Prof. U. C. Joshi is retired professor of PRL, Ahmedabad. His has diverse research interests: AGN, start clusters, planetary science, instrumentation, etc.



[77] Topic: PHASE-RESOLVED XMM-NEWTON AND SWIFT OBSERVATIONS OF WR 25

Speaker: Jeewan Ch Pandey
Affiliation: ARIES, Nainital
Date (yyyy-mm-dd): 2014-05-05
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: In this talk I will present an analysis of long-term X-ray and optical observations of the Wolf-Rayet binary WR 25. Using archival data from observations with the XMM-Newton and the Swift observatories spanning over ~10 years, we show that WR 25 is a periodic variable in X-rays with a period of 208 +/- 3 days. X-ray light curves in the 0.5-10.0 keV energy band show phase-locked variability, where the flux increased by a factor of ~2 from minimum to maximum, being maximum near periastron passage. The light curve in the soft energy band (0.5-2.0 keV) shows two minima indicating the presence of two eclipses. However, the light curve in the hard energy band (2.0-10.0 keV) shows only one minimum during the apastron passage. The X-ray spectra of WR 25 were explained by a two-temperatures plasma model. Both the cool and the hot plasmas were constant at 0.628+/-0.008 and 2.75+/-0.06 keV throughout an orbital cycle, where the cooler plasma could be due to the small scale shocks in a radiation driven outflow and the high temperature plasma could be due to the collision of winds. The column density varied with the orbital phase and was found to be maximum after the periastron passage, when the WN star is in front of O star. The abundances of WR 25 were found to be non-solar. Optical V-band data of WR 25 also show the phase-locked variability, being at maximum near periastron passage. The results based on the present analysis indicate that WR 25 is a colliding wind binary where the presence of soft X-rays is attributed to individual components; however, hard X-rays are due to the collision of winds.


About Speaker: Scientist at ARIES



[76] Topic: PHASE-RESOLVED XMM-NEWTON AND SWIFT OBSERVATIONS OF WR 25

Speaker: Jeewan Ch Pandey
Affiliation: ARIES, Nainital
Date (yyyy-mm-dd): 2014-05-05
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: In this talk I will present an analysis of long-term X-ray and optical observations of the Wolf-Rayet binary WR 25. Using archival data from observations with the XMM-Newton and the Swift observatories spanning over ~10 years, we show that WR 25 is a periodic variable in X-rays with a period of 208 +/- 3 days. X-ray light curves in the 0.5-10.0 keV energy band show phase-locked variability, where the flux increased by a factor of ~2 from minimum to maximum, being maximum near periastron passage. The light curve in the soft energy band (0.5-2.0 keV) shows two minima indicating the presence of two eclipses. However, the light curve in the hard energy band (2.0-10.0 keV) shows only one minimum during the apastron passage. The X-ray spectra of WR 25 were explained by a two-temperatures plasma model. Both the cool and the hot plasmas were constant at 0.628+/-0.008 and 2.75+/-0.06 keV throughout an orbital cycle, where the cooler plasma could be due to the small scale shocks in a radiation driven outflow and the high temperature plasma could be due to the collision of winds. The column density varied with the orbital phase and was found to be maximum after the periastron passage, when the WN star is in front of O star. The abundances of WR 25 were found to be non-solar. Optical V-band data of WR 25 also show the phase-locked variability, being at maximum near periastron passage. The results based on the present analysis indicate that WR 25 is a colliding wind binary where the presence of soft X-rays is attributed to individual components; however, hard X-rays are due to the collision of winds.


About Speaker: Scientist at ARIES



[75] Topic: Regional modeling of air pollutants in South Asia: present status and future directions

Speaker: Dr. Rajesh Kumar
Affiliation: Advanced Study Program (ASP), National Center for Atmospheric Research (NCAR), B
Date (yyyy-mm-dd): 2014-05-20
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: The concentrations of key trace gases and aerosols are increasing rapidly in the atmosphere of South Asia owing to growing population and associated increase in human activities. These rising concentrations can potentially affect the air quality, atmospheric chemistry, agriculture, ecosystems, freshwater resources and climate, and therefore pose a serious threat to the health, food and water security of billions of people living in South Asia. A recent study shows that premature mortality rates in South Asia due to air pollution are among highest in the world. Therefore, it is very important to understand the processes controlling the distribution and variability of pollutants in this region. However, the available in situ observations of trace gases and aerosols lack sufficient space-time coverage to address this problem and thus use of chemical transport model results and satellite observations becomes essential to advance our understanding of air pollution in this region. In this talk, I will begin with an overview of air pollution problem in South Asia and show how this problem is different from what other parts of the world are facing. Next, I will illustrate the potential of Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) to help the interpretation of in situ and satellite observations in South Asia through application of WRF-Chem to three problems of scientific interest. These include simulations of wintertime carbon monoxide (CO) pollution, a typical pre-monsoon season dust storm, and black carbon aerosol distribution. In the end, I will highlight the scope of improvement in present set-up of WRF-Chem and present an outlook towards future research in South Asia.


About Speaker: He is ASP fellow at NCAR, Boulder, USA.



[74] Topic: Influence of short period gravity waves in vertical transport of aerosols during daytime boundary layer evolution over Central Himalayan region: A case study

Speaker: K K Shukla
Affiliation: ARIES
Date (yyyy-mm-dd): 2014-05-01
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: In this study, we present a case of 16 October 2011 to show the first observational evidence of influence of short period gravity waves in aerosol transport during daytime over Central Himalayan region. Doppler lidar data is utilized to address the daytime boundary layer evolution and related aerosol dynamics over the site. Boundary layer height is estimated by wavelet covariance transform method and found to be ~ 0.7 km AGL. AOD observations during daytime revealed an asymmetry showing clear enhancement during afternoon hours as compared to forenoon. Interestingly, Fourier and wavelet analysis showed similar 50-90 min short period gravity wave signatures dominant during afternoon hours. Moreover, our observations showed gravity waves are dominant within boundary layer implying that the daytime boundary layer dynamics is playing a vital role in transporting the aerosols from surface to boundary layer top. Similar modulations are also evident in surface parameters like Temperature, RH and wind speed indicating these waves are associated with the dynamical aspects over Himalayan region. Finally, time evolution of RHI snapshots during daytime showed strong upward velocities especially during afternoon hours implying that the transportation of aerosols by convective processes are dominant through short period gravity waves to boundary layer top over the site. Our observations should shed some light in the current understanding of wave induced daytime convective boundary layer dynamics over Himalayan region.


About Speaker: Research Scholar working in the field of Atmospheric Sciences



[73] Topic: Bio-energy from Waste Water Treament

Speaker: Dr. Y V Swamy
Affiliation: Indian Institute of Chemical Technology (IICT), Hyderabad
Date (yyyy-mm-dd): 2014-04-16
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: Chemical and allied industries in India are poised for higher growth in the coming decade. Due to stringent environmental regulations, the market for technologies related to treatment of industrial waste and its utilization is expected to grow further. Appropriate technologies, specifically the ones that recover value added products, shall find market without much difficulty. A sustainable hybrid waste/wastewater treatment methodology, capable of removing multiple pollutants along with renewable energy generation is another area that has immense potential. Conventional treatment processes often fail due to varied characteristics of the waste water. Anaerobic dark fermentation treatment produces methane, which is again a greenhouse gas. Hence, a novel approach has been made to produce hydrogen using pre-treated mixed culture. An effort also has been made to produce bio-plastic and bio-electric from the anaerobically treated waste water. By integrating these process steps COD, BOD and TDS could be reduced to acceptable limits besides producing energy by these dual approach. More details will be presented during the talk.


About Speaker: Speaker is a Chief Scientist and Head of Bioengineering and Environmental Centre (BEEC) at Indian Institute of Chemical Technology (IICT), Hyderabad. He is actively involved on Climate Change and Environmental research.



[72] Topic: Open Star Clusters in galaxy

Speaker: Rohit Nagaori
Affiliation: IIST
Date (yyyy-mm-dd): 2014-04-10
Time: 16:00hr
Venue: Auditorium

Abstract: The aim of our project is to study the statistical distribution of the various cluster parameters and the correlation between them. For that purpose, we have prepared a dataset consisting of the various parameters of clusters with the help of Kharchenko et al.(2013) catalogue. We have studied the statistical distribution of parameters such as diameter, age, metallicity as well as correlations between various parameters such as mass with respect to age and diameter of clusters. We also studied the distribution of open clusters in longitudes as well as their spatial distribution in galactic plane.


About Speaker: Rohit Nagaori is a final semester B. Tech. student at IIST Trivandrum.



[71] Topic: Photometric evolution of type IIP supernova SN 2004dj

Speaker: Rohit Patil
Affiliation: IIST
Date (yyyy-mm-dd): 2014-04-10
Time: 15:30hr
Venue: Auditorium

Abstract: Photometric evolution of a type IIP supernova SN 2004dj is studied in this project.


About Speaker: Rohit Patil is a final semester B. Tech. student at IIST Trivandrum.



[70] Topic: Variations in Hydrocarbons over the central Himalayas and the Indo-Gangetic Plain.

Speaker: Tapaswini Sarangi
Affiliation: ARIES
Date (yyyy-mm-dd): 2014-03-31
Time: 14:30hr
Venue: New Auditorium

Abstract: Thesis material of Tapaswini.


About Speaker: Tapaswini Sarangi submitted her thesis done under Dr. Manish Naja. She was a project student under Dr. Naja, and now has applied for regular ARIES post-doctoral position.



[69] Topic: MHD wave modes and their energy flux in the realistic 3D magnetic flux tube(s) configurations

Speaker: Viktor Fedun
Affiliation: The University of Sheffield,
Date (yyyy-mm-dd): 2014-03-25
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: Photospheric motions, such as granular buffeting or vortices at the foot-point of magnetic flux tubes, could excite MHD waves, which propagate upwards though the solar atmosphere towards corona. In this talk I will show the results of 3D numerical simulation of generation and propagation of slow/fast magnetoacoustic and torsional Alfv'en modes in the localised waveguides and determine the energy flux they carry along the magnetic field lines. Also, the new analytical approach in construction of a system of multiple magnetic flux tubes, for example, pair of open tubes and complex mixed open tube configurations with curvature and asymmetry, will be discussed. This method provides an opportunity to build a range of analytical models of magnetic field configurations that will most realistically capturing magnetic structures of the lower solar atmosphere. The model includes a number of free parameters, which makes the solution applicable to a variety of other physical problems and it may therefore be of more.


About Speaker: Dr. Fedun is working in The University of Sheffield. His research interest is the mathematical modelling of physics of solar/space plasmas, sun-solar wind, solar-terrestrial systems.



[68] Topic: MHD wave modes and their energy flux in the realistic 3D magnetic flux tube(s) configurations

Speaker: Viktor Fedun
Affiliation: The University of Sheffield,
Date (yyyy-mm-dd): 2014-03-25
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: Photospheric motions, such as granular buffeting or vortices at the foot-point of magnetic flux tubes, could excite MHD waves, which propagate upwards though the solar atmosphere towards corona. In this talk I will show the results of 3D numerical simulation of generation and propagation of slow/fast magnetoacoustic and torsional Alfv'en modes in the localised waveguides and determine the energy flux they carry along the magnetic field lines. Also, the new analytical approach in construction of a system of multiple magnetic flux tubes, for example, pair of open tubes and complex mixed open tube configurations with curvature and asymmetry, will be discussed. This method provides an opportunity to build a range of analytical models of magnetic field configurations that will most realistically capturing magnetic structures of the lower solar atmosphere. The model includes a number of free parameters, which makes the solution applicable to a variety of other physical problems and it may therefore be of more


About Speaker: Dr. Fedun is in The University of Sheffield. His research interest is mathematical modelling of physics of solar/space plasmas, sun-solar wind and solar-terrestrial systems.



[67] Topic: Observatory Control Software for 3.6m Telescope

Speaker: Bhavya Kaushik
Affiliation: Manipal University Jaipur
Date (yyyy-mm-dd): 2014-02-28
Time: 15:30hr
Venue: Auditorium

Abstract: A primary design of GUI, Command Interface, OCS-TCS Interface, OCS-DCS Interface, OCS-ICS Interface, Authentication System, Logging System, Remote Access, Feedback System of the Observatory Control Software for 3.6m Telescope using Qt framework. This work will be discussed in this talk.


About Speaker: Mr. Bhavya Kaushik is student of M.Tech. final year at Manipaul University Jaipur. He is working as project trainee at ARIES for last seven months. He is working on software development for 3.6m Telescope OCS.



[66] Topic: Probing energetics of solar flares from multi-wavelength emission

Speaker: Arun Kumar Awasthi
Affiliation: Physical Research Laboratory
Date (yyyy-mm-dd): 2014-01-10
Time: 15:30hr
Venue: New Auditorium

Abstract: Solar flares are sudden and bursty emissions from the atmosphere of the Sun. Temporal evolution of the flares consists of three phases viz. Precursor, impulsive and gradual. Latter two phases have been studies extensively, however underlying physical processes of energy release during the precursor phase are not yet fully understood owing to lack of high cadence observations. I will present the current understanding on this phase of flare emission as well as my work on the same. Further, I will also present the thermal characterisation of flare plasma in view of its iso/multi-thermal nature.


About Speaker: Completed his PhD from Physical Research Laboratory, and applied for post-doctoral position in ARIES.



[65] Topic: Near-infrared study of classical novae

Speaker: Ashish Raj
Affiliation: Physical Research Laboratory
Date (yyyy-mm-dd): 2014-01-07
Time: 15:30hr
Venue: New Auditorium

Abstract: The classical novae are close binary systems with a late-type main sequence star (the secondary) transferring material via Roche lobe overflow to a companion star (the primary). Novae brighten by 10 - 12 magnitudes in a few hours and subsequently fade back to the original faint level over a period lasting several months to years. The results obtained from the IR observations will be presented. The system parameters of the observed novae, like the distance to the nova, absolute magnitude, expansion velocity of the ejecta, mass of the ejecta and gas to dust ratio are estimated. The dust formation and the detection of first overtone emission bands of CO in these novae will be discussed.


About Speaker: Dr. Ahish Raj is a post-doc in PRL, and has applied for post-doctoral position in ARIES.



[64] Topic: VERTICAL PROFILING OF AEROSOL OVER MANORA PEAK USING MPL: GVAX CAMPAIGN

Speaker: Shishir Kumar Singh
Affiliation: B H U, Varanasi
Date (yyyy-mm-dd): 2013-12-24
Time: 11:30hr
Venue: Auditorium

Abstract: The variability in aerosol vertical distribution during the transition phase from winter to spring season was studied. We incorporated the data collected by the micro-pulse LiDAR (MPL) (Feb-March 2012) operated as part of GVAX-campaign. A comparison of aerosol backscatter profile obtained from GVAX MPL and one other collocated LiDAR (LAMP) at ARIES has also been studied.


About Speaker: Mr. Shishir is a student of M.Sc. Tech. final year at BHU Varanasi



[63] Topic: Latitudinal variability in CALIPSO derived aerosol vertical profile over the central Himalayas and IGP

Speaker: Pratima Gupta
Affiliation: B H U, Varanasi
Date (yyyy-mm-dd): 2013-12-24
Time: 11:00hr
Venue: Auditorium

Abstract: In this study we analyzed data collected by the space-born LiDAR (CALIOP) on-board the satellite CALIPSO. The latitudinal variability in vertical distribution of aerosols (backscatter coefficient and depolarization ratio) has been studied during January to December, for the year 2012.


About Speaker: Miss Pratima is a student of M.Sc. Tech. final year at BHU Varanasi



[62] Topic: DISTANCE DETERMINATION TO EIGHT GALAXIES USING EXPANDING PHOTOSPHERE METHOD

Speaker: Subhash Bose
Affiliation: ARIES
Date (yyyy-mm-dd): 2013-12-27
Time: 15:30hr
Venue: Auditorium

Abstract: Type IIP supernovae are recognized as independent extragalactic distance indicators, however, keeping in view of the diverse nature of their observed properties as well as the availability of good quality data, more and newer events need to be tested for their applicability as a reliable distance indicators. We use early photometric and spectroscopic data of eight type-IIP SNe to derive distances to their host galaxies using the expanding photosphere method (EPM). For five of these, EPM is applied for the first time. In this work, we improved EPM application by using synow estimated velocities and by semi-deconvolving the broadband filter responses while deriving color temperatures and black-body angular radii. We find that the derived EPM distances are consistent with that derived using other redshift independent methods.


About Speaker: Mr. Subhash Bose is SRF at ARIES.



[61] Topic: A spectroscopic study of cool pulsating A and F stars within Indo-Russian DST-RFBR project

Speaker: Dr. Evgeney Semenko
Affiliation: Special Astrophysical Observatory (SAO), Russia,
Date (yyyy-mm-dd): 2013-12-13
Time: 15:30hr
Venue: Auditorium

Abstract: An international bilateral Indo-Russian project is being supported by DST, Govt of India and RFBR, Russia aiming for the complex study of pulsation in A and F stars those discovered under the Nainital-Cape photometric survey. The current talk is based on the new results of spectroscopic study of three cool A stars with different rotational velocity. We have shown that chemical abundances of this programme objects are typical for delta Sct-type and metallic-line stars.


About Speaker: Dr. Semenko is working as a researcher/scientist at SAO, Russia.



[60] Topic: Nonlinear analysis of Spatiotemporal data: Applications in Biology

Speaker: Naveen Kumar Bhatraju
Affiliation: University of Delhi
Date (yyyy-mm-dd): 2013-11-27
Time: 11:00hr
Venue: Auditorium

Abstract: Weather, climate, earthquake and forex are a few examples of a vast list of complex real world dynamical systems where forecast of extreme events that would occur in future is of great value. Accurate prediction of such events requires a critical understanding of the dynamics of these complex systems. The introduction of nonlinear time series analysis has given significant insights into the temporal patterns in the dynamics of the aforementioned systems. There are many nonlinear analysis methods proposed for analyzing a given time series including, but not limited to, fluctuation analysis, synchronization, entropy and recurrence analysis. In the present talk, I will be discussing some of the aforementioned techniques which were used by us for analysis of biological and physical systems.


About Speaker: Working at University of Delhi.



[59] Topic: Identification of Coronal Funnels On the Basis of Doppler Velocity, Line Width and Density in the Quiet Sun and Coronal Hole

Speaker: Pradeep Kayshap
Affiliation: ARIES, Nainital, India
Date (yyyy-mm-dd): 2013-12-10
Time: 15:30hr
Venue: New Auditorium

Abstract: Coronal funnels, which originates from the networks at the photosphere, have great importance in terms of the mass up flows from lower to upper solar atmosphere. We have studied a North Polar Coronal Hole (NPCH) observation, which was observed on 10 October 2007 by Extreme Ultraviolet Imaging Spectrometer (EIS) onboard Hinode, to identify the coronal funnels in the observed region. By the Gaussian fitting technique, we have estimated three basis parameters (e.g., Doppler velocity, FWHM, Intensity) on each location of the observed region. Extra FWHM locations (i.e., above a threshold level) have been identified in quiet sun (QS), quiet sun with coronal hole boundary (QSCH) and coronal hole (CH) regions. For the density measurement, we have used the intensity ratio of two density sensitive Fe XII lines and CHIANTI atomic data. On the basis of the variations of the parameters (e.g.,intensity,Doppler velocity,density), we have shown that the excess width regions in the quiet sun are the coronal funnels. In the QSCH and CH regions, we have not found the favorable results to say that the excess width locations in these regions are the coronal funnels. We have also found that plasma up flow starts at log 6.0 K and log 5.8 K in the quiet sun and coronal holes respectively. Study of the temperature dependent behaviour of the nonthermal velocity is a forefront research in the solar physics now-a-days. In present analysis, nonthermal velocity decreases from Transition Region (TR) up to corona in the coronal hole as well as quiet sun. With the help of some previous results of nonthermal velocities, we have found that nonthermal velocity increase with temperature but after a certain temperature it decrease further. We have shown that Alfven wave propagation and dissipation as well as the prevalent occurrence of nano-flares at O VI formation temperature are two most probable responsible mechanisms for the explanation of nonthermal velocity.


About Speaker: Pradeep Kayshap is the SRF working in the field of Solar Physics.



[58] Topic: STELLAR PULSATION: A NON LINEAR PERSPECTIVE

Speaker: Prof. M. K. Das
Affiliation: University of Delhi
Date (yyyy-mm-dd): 2013-11-25
Time: 15:30hr
Venue: Auditorium

Abstract: We have studied the temporal characteristics of different nonlinear stellar pulsation models in the nonlinear framework. In general the temporal behavior i.e., time series of amplitude variation are non-stationary and therefore the linear framework becomes inadequate for further characterization. Therefore, we have used wavelet analysis to investigate their characteristics in the time-frequency domain. Further the time series obtained in most of these model suggests period doubling and chaotic behavior for certain control parameters, in the phase space. As usually only one observational parameter is measured in a given setting, it is used to reconstruct an attractor in the phase space using phase space reconstruction method. Further characterization of the attractor and hence the time series ,obtained for various models, have been made using the recurrence quantification analysis (RQA).


About Speaker: Prof. Das is at Institute of Informatics & Communication University of Delhi South Campus.



[57] Topic: Synoptic Maps of Solar Vector Magnetic Fields from VSM/SOLIS instrument at NSO: First Results

Speaker: Sanjay Gosain
Affiliation: NSO, Tucson, USA
Date (yyyy-mm-dd): 2013-11-14
Time: 15:30hr
Venue: New Auditorium

Abstract: Full-disk vector magnetic field measurements of the Sun are now routinely carried out at National Solar Observatory, Tucson, USA, since the beginning of cycle 24. In order to understand the role of magnetic field in production of flares and coronal mass ejections (CMEs) as well as its evolution with 11 year solar cycle we need continuous uninterrupted measurements of solar magnetic field. Space based measurements by missions like SOHO/MDI and SDO/HMI have limited lifetime and are prone to non-repairable failures. Ground based measurements on the other hand have long lifetimes and can be easily repaired and maintained. I will describe the new fulldisk observations of the vector magnetic fields by SOLIS VSM at NSO and the new type of synoptic maps that are produced from these observations . I will also present few results from these measurements relevant to large scale patterns of magnetic fields and their helicity.


About Speaker: Dr. Sanjay Gosain is working at NSO, Tucson, USA. He is well known for the observations and modelling of the solar photospheric magnetic fields, and their role in the various types of eruptive phenomena.



[56] Topic: SOLAR FILAMENTS AS INDICATORS OF CME PROBABILITY

Speaker: Boris Filippov
Affiliation: Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagatio
Date (yyyy-mm-dd): 2013-11-12
Time: 15:30hr
Venue: New Auditorium

Abstract: The onset of a CME is not preceded by any specific form of activity that could be recognized several days before the event. The cause of eruption is more likely in properties of coronal magnetic field equilibrium, possibly in the rapid growth of instability. The most probable initial magnetic configuration of a CME is a flux rope consisting of twisted field lines which fills the whole volume of the dark cavity stretched in the corona along the photospheric polarity inversion line. A coronal cavity is well recognized in coronal images only when its axis is directed along the line-of-sight; otherwise it is screened by surrounding bright coronal loops. Cold dense prominence matter accumulates in the lower parts of helical flux tubes, which serve as magnetic traps in the gravitation field. So, prominences and filaments are good tracers of the flux ropes in the corona long before the beginning of eruption. A twisted flux rope is held by the tension of field lines of photospheric sources until parameters of the system reach critical values and catastrophe happens. The flux rope height above the photosphere is one of these parameters and it is revealed by the height of the filament. There is a critical height in the given coronal magnetic field that the flux rope cannot exceed being in stable equilibrium. We found that many eruptive prominences were near the limit of stability a few days before eruptions. A filament eruption on 2010 October 21 observed from three different viewpoints by the Solar Terrestrial Relations Observatory and the Solar Dynamic Observatory is analyzed in detail by invoking also data from the Solar and Heliospheric Observatory and the Kanzelhoehe Solar Observatory. The position of the filament just before the eruption at the central meridian not far from the center of the solar disk was favorable for photospheric magnetic field measurements in the area below the filament. Because of this, we were able to calculate with high precision the distribution of the coronal potential magnetic field near the filament. We found that the filament began to erupt when it approached the height in the corona where the magnetic field decay index was greater than 1. We believe that a comparison of the measured heights of filaments with the calculated critical heights could be a basis for predicting filament eruptions and following CMEs.


About Speaker: Dr. Boris Fillipov is the head of laboratory of solar physics at IZMIRAN, Troitsk, Russia. He is well known for the modelling and observations of the solar eruption pre-cursors, e.g., solar filaments. He is visiting ARIES as a Russian PI of ongoing DST-RFBR project.



[55] Topic: GUI and Command Interface Design for 3.6m Observatory Control Software

Speaker: Bhavya Kaushik
Affiliation: Manipal University Jaipur
Date (yyyy-mm-dd): 2013-10-11
Time: 15:30hr
Venue: Auditorium

Abstract: A primary design of GUI of the Observatory Control Software for 3.6m Telescope and command interface design have been implemented using Qt framework. This work will be discussed in this talk.


About Speaker: Mr. Bhavya Kaushik is student of M.Tech. final year at Manipaul University Jaipur. He is working as project trainee at ARIES for last two months. He is working on software development for 3.6m Telescope. He is working on GUI and command interface design and OCS-TCS interface design.



[54] Topic: BLACK HOLES OF GENERAL RELATIVITY

Speaker: Dr. G. Srinivasan
Affiliation: Former Jawaharlal Nehru Fellow, Raman Research Institute (Retired)
Date (yyyy-mm-dd): 2013-10-04
Time: 11:00hr
Venue: Auditorium

Abstract: The details about BLACK HOLES OF GENERAL RELATIVITY will be discuss and the colloquium will be non technical.


About Speaker: Dr. G. Srinivasan is Former Jawaharlal Nehru Fellow and retired from Raman Research Institute, Bangalore.



[52] Topic: Significance of MHD Seismology in the Astrophysical Plasma

Speaker: Dr. A.K. Srivastava
Affiliation: ARIES, Nainital
Date (yyyy-mm-dd): 2013-10-08
Time: 15:30hr
Venue: New Auditorium

Abstract: The stable fluxtubes possessing the ionized plasma coupled with magnetic field, when perturbed from their equilibrium, can support the evolution of various tubular MHD modes (e.g., kink, sausage, torsional, and slow waves). These modes are now ubiquitous in the various astrophysical plasmas, e.g., the solar and stellar coronae. The detection of these MHD modes are important keeping the view of their physical properties that can be utilized in deriving many crucial local plasma conditions where they excite. In the present paper, we review the state-of-art of this continuously developing new sub-field in the Astrophysics. We present the detection of MHD modes in coronae of Sun and Sun-like stars and use of the principle of MHD seismology to understand some local physical conditions there (e.g., magnetic field) that can not be determined by classical methods. We conclude that the refinement in the MHD seismology of solar corona is also providing the best analogy to develop the stellar seismology of magnetically active similar stars to deduce the local physical conditions of their coronae.


About Speaker: Dr. A.K. Srivastava is working in ARIES as a Scientist in the field of Solar Physics. His primary research interest is to understand the transients (e.g., spicules, jets, and large-scale eruptions) and MHD phenomena (waves, heating processes, reconnection, instabilities) in the solar atmosphere under observational and theoretical base-line.



[51] Topic: Errors in astronomical observations due to motion of the observer and the physical justification against dark flow

Speaker: Mukesh Kumar Vyas
Affiliation: Aries
Date (yyyy-mm-dd): 2013-10-01
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: The talk is designed to present my initial work done in theoretical cosmology. The analysis has two implications, The effect of the motion of the observer induces a certain amount of error in the observational astronomy. The relation of this effect is derived and a need for correction in the position (up to 5% of a degree in angular shift in the coordinates)of cosmic objects is proposed due to our cosmic motion around the Milky Way. As the second implication, the results of the analysis will help us to solve the debate over physical existence of the dark flow and and our motion under CMB dipole with predicted speed 630km/sec. Primary outcomes provide negative results for the validity of Dark flow. If further analysis of cosmic structure follows primary indications (which is the next step of the work) it will be a strong evidence against multiverse concept in modern cosmology.


About Speaker: Research scholar at ARIES



[50] Topic: HI gas in absorption towards the central regions of radio galaxies

Speaker: Dr. Yogesh Chandola
Affiliation: NCRA, Pune
Date (yyyy-mm-dd): 2013-10-03
Time: 15:30hr
Venue: New Auditorium

Abstract: In radio galaxies, an understanding of the gaseous components in their environments as well as in the nuclear regions could provide insights towards understanding the triggering of radio activity, understanding fueling processes, probing jet-cloud interactions and also constraining orientation dependent unification schemes. Detection of HI via 21-cm absorption lines towards compact radio sources (GPS, CSS and compact cores of the larger radio sources) has been an important tool to study this cold neutral component of the circumnuclear gas in the host galaxies of AGN. This gas could be either part of the interstellar medium (ISM) of the host galaxy, or be a constituent of the circumnuclear tori or disk in the central region of the host. I present the results of HI 21-cm absorption line studies towards the central regions of radio galaxies. These observations were made with the Giant Metrewave Radio Telescope(GMRT) to detect HI gas via absorption, study the kinematics and distribution of this cold atomic gas in their central regions. We detected new HI absorption towards seven radio sources in our studies done for a sample of low luminosity nearby compact CSS & GPS radio sources. Within the uncertainties, the detection rates and column densities are similar to the more luminous objects, with the GPS objects exhibiting a higher detection rate than for the CSS objects. In HI absorption studies towards the cores of larger radio sources, considering observations of similar sensitivity, we find that the detection rate of HI absorption towards the cores of larger (>15 kpc) sources is only ∼15 per cent, compared with ∼57 per cent for CSS and GPS objects, suggesting an evolution in the gaseous content of the host galaxies as the radio sources age and grow in size. I will also summarize the results of our HI absorption observations towards the central regions of rejuvenated radio sources.


About Speaker: Post Doctoral Fellow in NCRA, Pune.



[49] Topic: Black hole Accretion in Schwarzschild Metric

Speaker: Golam Mafuz
Affiliation: IIT Kharagpur
Date (yyyy-mm-dd): 2013-09-20
Time: 15:30hr
Venue: New Auditorium

Abstract: For any specific energy and specific angular momentum there may exist multiple critical point. For a specific energy and angular momentum, I have plotted the Mach number as a function of distance.


About Speaker: Completed MSc from IIT Kharapur.



[48] Topic: REVISITING NEWTON’S LAWS: POSSIBLE MODIFICATION AND AMAZING COSMOLOGICAL CONSEQUENCES

Speaker: Amitabha Ghosh
Affiliation: Platinum Jubilee Senior Scientist of The National Academy of Sciences India & Ho
Date (yyyy-mm-dd): 2013-09-13
Time: 11:00hr
Venue: ARIES Auditorium

Abstract: Newton’s Laws of motion and universal gravitation constitute the foundation of almost all branches of science and engineering. Mostly, these are introduced at the senior levels in the schools and the students practice applying these laws to many problems. Apparently these laws look fine and without any problem. But as one rarely returns to ponder over these laws seriously at senior levels, the serious problems associated with these laws remain unnoticed. This lecture proposes a return to the Newton’s Laws of motion and universal gravitation to examine the situation. In the first part of the talk the difficulties with these laws will be discussed and some modifications will be suggested. It will be shown how the difficulties melt away and very profound consequences emerge. In the second part of the talk the modified law will be applied to a number of astrophysical and solar system mechanics problems. It will be very interesting to see how in all cases the proposed extended Newton’s laws can resolve a number of unexplained phenomena and finally results in a very profound consequence so far as the model of our universe is concerned.


About Speaker: Amitabha Ghosh received his Bachelor of Engineering and Master of Engineering degrees from Bengal Engineering College, Shibpur, (Calcutta University) in 1962 and 1964, respectively. He joined the Mechanical Engineering Department of this college as a Lecturer in 1965 May and continued his doctoral research finally receiving the Doctorate degree from Calcutta University in 1969. He joined IIT Kanpur in January 1971 as an Assistant Professor of Mechanical Engineering and became Professor in 1975 June. From 1977 to 1978 he spent at the Technical University Aachen with Alexander von Humboldt Foundation senior fellowship. From 1997 to 2002 he served IIT Kharagpur as the Director and subsequently returned to his Professorial position at Kanpur where he continued up to 2006 till his retirement. After retirement from IIT Kanpur he worked as a Senior Scientist of the Indian National Science Academy, New Delhi and Honorary Distinguished Professor at both IIT Kanpur and Bengal Engineering & Science University, Shibpur. Currently he is a Platinum Jubilee Senior Scientist of the National Academy of Sciences, India, Allahabad and also an Honorary Distinguished Professor at Bengal Engineering & Science University, Shibpur. His research and academic interests are in Basic Mechanics, Kinematics and Dynamics, Advanced Manufacturing and Robotics. He has guided more than 75 M Tech and 18 PhD students and published about 125 research papers.



[47] Topic: Confined Partial Filament Eruption and its Reformation within a Stable Magnetic Flux Rope

Speaker: Navin C Joshi
Affiliation: ARIES
Date (yyyy-mm-dd): 2013-09-10
Time: 15:30hr
Venue: ARIES AUDITORIUM

Abstract: In this paper, we present an observation of the confined upward motion of core cooler plasma of a filament that remains within a stable magnetic configuration during its activation. Later it exhibits a rapid reformation along the same magnetic channel within ≈2 hours after the eruption on 4 August 2012. Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA), Solar TErrestrial RElations Observatory/Sun Earth Connection Coronal and Heliospheric Investigation (STEREO/SECCHI) and Global Oscillation Network Group (GONG) Hα observations have been analyzed to investigate the physical mechanism of this plasma dynamics of filament, which shows the sinistral magnetic orientation with positive sign of magnetic helicity. From the GONG Hα observations, we find that the filament plasma gets into its dynamic motion at around 11:20 UT from the middle part of the filament towards the north-west direction with an average speed of ≈100 km/s. Small brightening underneath of it shows possibly the signature of low atmospheric reconnection below the filament eruptive part. In SDO/AIA 171 A images, we observe an activation of right-handed helically A twisted magnetic flux rope that contains the filament material and confines it during its dynamical motion. The motion of the cool plasma of the filament core stops after traveling a distance of around ≈215 Mm from the point of eruption towards north-west. Some of the plasma moves towards right foot point of the flux rope, while most of the plasma returnes back after 12:00 UT towards the left foot point in order to reform the filament with an average speed of ≈60 km/s within the stable magnetic structure. From the coronal magnetic field decay index n calculation near the flux rope axis, it is evident that the whole filament axis lies within the domain of stability (i.e., n < 1), which infers the filament stability in spite of strong disturbances at its eastern foot point.


About Speaker: Dr. Navin C Joshi is post-doc at ARIES and works in a field of Solar Physics.



[46] Topic: Studies of dust properties and the importance of magnetic fields using optical and NIRpolarimetry.

Speaker: C. Eswaraiah
Affiliation: ARIES
Date (yyyy-mm-dd): 2013-09-06
Time: 11:00hr
Venue: ARIES AUDITORIUM

Abstract: I will present results based on the work done for the last six months during my PDF tenure. During this period, I have worked on various projects related to studies of dust grain properties and the role of magnetic fields in connection with the formation of clouds, their evolution and collapse and finally the star-formation processes. I briefly present about the structure function analysis on the measured polarization angles towards a dark globule LDN1570 and its significance in understanding the importance of magnetic fields in rendering the cloud stability against gravity and turbulence. Then, I will present our recent results based on the near-infrared (NIR) polarimetric observations of a starforming region NGC 1893. Analysis yields important clues regarding the uniform alignment of dust grains (and hence high polarization efficiency) in accordance with our previous results based on optical polarimetry (Eswaraiah et al. 2011). I will discuss how the magnetic field orientation inferred using J and H-band polarization angles may give important clues regrading the impact of ionizing radiation on the surrounding medium, and the correlation between the magnetic field structure with the starformation activity in NGC 1893 region. I will also present the preliminary results based on the


About Speaker: He is Post -doc at ARIES and working on polarimetric study of star forming regions.



[45] Topic: Molecular forms of PAH in diverse Astrophysical objects

Speaker: Shantanu Rastogi
Affiliation: University of Gorakhpur
Date (yyyy-mm-dd): 2013-09-04
Time: 15:30hr
Venue: Auditorium

Abstract: The mid infrared bands and their relation to aromatic molecules i.e. the PAH hypothesis will be discussed. The feature variations are related to object type and have been correlated with different PAH populations. Study of different varieties of PAHs and emission models to match the IR bands will be presented. Possible evolution of PAH varieties and their relation to object type will be discussed.


About Speaker: Professor at Department of Physics, University of Gorakhpur, Gorakhpur. Dr. Rastogi works on astrophysics.



[44] Topic: Deep optical and near-infrared survey of the stellar contents of Sh2-311 region

Speaker: Ram Kesh Yadav
Affiliation: ARIES
Date (yyyy-mm-dd): 2013-09-03
Time: 15:30hr
Venue: ARIES auditorium

Abstract: The stellar content and environment of the Sh2-311 region have been studied using the deep optical and near-infrared (NIR) observations. The region contains three clusters, viz. NGC 2467, Haffner 18 and Haffner 19. NGC 2467 and Haffner 19 are found to be located in the Perseus arm at the distances of 5.0±0.4 kpc and 5.7±0.4 kpc, respectively whereas cluster Haffner 18 is located at the distance of 11.2±1.0 kpc. The NGC 2467 and Haffner 19 clusters might have been formed from the same molecular cloud, whereas the the cluster Haffner 18 is located in the outer galactic arm Norma-Cygnus. On the basis of deep NIR observations we have identified 73 young stellar sources (YSOs) with NIR-excess stars. The estimated ages and masses of these YSOs are in the range of 0.1-5.0 Myr and 0.3-3.5 M_sun, respectively suggesting that these sources could be T-Tauri stars. Spatial distribution of YSOs shows that some of the YSOs are distributed along the 8 µm emission contours derived from Spitzer IRAC observation, whereas a significant number of YSOs are clustered towards the eastern border of the 8 µm contours. The dynamical age of the ionized region, spatial distribution of YSOs, and mean age of the YSOs, (∼1.3 Myr) suggest for a triggered star formation in the Sh2-311 region probably due to the collect and collapse process. The IMF of the YSOs is found to be flat (Γ=0.08±0.22).


About Speaker: SRF at ARIES



[43] Topic: Study of Solar Eruptive Phenomena and their Interplanetary Consequences

Speaker: Navin Chandra Joshi
Affiliation: ARIES
Date (yyyy-mm-dd): 2013-08-27
Time: 15:30hr
Venue: New Auditorium

Abstract: In this talk, I will discuss my main research work during last one year in which I have contributed significantly. During the last one year I actively involved in various research and developmental activities in Solar Group at ARIES. We have studied a huge solar eruptive event on 23 January 2012 using multiwavelength data set and found the evidence of CME-CME interaction, which produced a huge solar energetic particle event of cycle 24 (paper I). I will also discuss another work in which I have investigated the relationship between the asymmetric filament eruption and coronal downflows and interpreted my observations with the self-consistent model of flux rope (paper 2). The filament stability and its quick reformation (paper 3) will also discussed in this talk. Apart form this I will also present my research and developmental activity, conference attended, paper presented and my future work at ARIES.


About Speaker: Post Doctoral Fellow in ARIES, who has completed 2 years.



[42] Topic: Research activities under the ABLN&C project: A part of NOBLE network under ISRO-GBP

Speaker: Raman Solanki
Affiliation: ARIES
Date (yyyy-mm-dd): 2013-08-22
Time: 16:30hr
Venue: Auditorium

Abstract: Under the ABLN &C project a Micro Pulse LiDAR and two ultrasonic anemometers have been installed over the Manora Peak, Nainital. The site is a part of the NOBLE (Network of Observatories for Boundary Layer Experiment) network, representing a complex topographical location. Measurement of vertical distribution of aerosols and clouds over Manora peak are being made since October 2011, with a LAMP (LiDAR for Atmospheric Measurement and Probing) system. The seasonal variability in vertical distribution of aerosol has been studied over this high altitude regional representative site. Elevated aerosol layers and clouds have also been studied to understand their radiative effects on the atmosphere. In order to study the atmospheric boundary layer processes over the complex topography of the central Himalayas, a meteorological tower has been setup over Manora peak, Nainital, with Ultrasonic anemometer at two levels (12 and 27m AGL). Continuous measurements are being made since 30 January 2013. The instrument measures the wind components and temperature at sampling rate of 25Hz. Through these measurements seasonal and diurnal variability of basic meteorological parameters, momentum flux and turbulence kinetic energy have been studied. Vertical winds play an important role in mountain meteorology, as they can bring pollutants, moisture, etc. from the nearby regions, and may also bring clean air from free troposphere to the site. Seasonal and diurnal variability of vertical wind have been studied for the first time at the site. The study will be crucial in quantifying the variability in anabatic and katabatic winds over Manora peak.


About Speaker: He is JRF in ARIES, under ISRO funded ABLN&C project with Atmospheric Science Group.



[41] Topic: Variabilities in Ozone and precursor at a high altitude site over the central Himalayas

Speaker: Tapaswini Sarangi
Affiliation: ARIES
Date (yyyy-mm-dd): 2013-08-22
Time: 15:15hr
Venue: ARIES Auditorium

Abstract: Diurnal variations in ozone do not show a daytime build up, while, CO and NOy generally show higher levels during daytime and lower levels during nighttime at Nainital. It is shown that the diurnal variations in these gases are mainly governed by the dynamical processes including upslope downslope mountain winds and the boundary layer evolution and associated convective mixing. This is confirmed by the simulated vertical wind and the boundary layer height using WRF model. Seasonal variations in ozone, CO and NOy at Nainital are characterized by spring maxima and summer-monsoon minima. This seasonality is found in good agreement with the variability of weather parameters. Seasonality in CH4 and light (C2-C5) NMHCs shows a late autumn and early winter maxima and summer monsoon minima. This has been attributed to the post monsoon pattern along with the long range transport of pollutants during winter while regional pollution along with biomass burning activities plays key role for springtime maxima of ozone, CO and NOy. The classification based on the air-mass residence time shows ozone, CO and NOy, levels of 57±14 ppbv, 206±125 ppbv, and 1856±1596 pptv in the continental and 25±11 ppbv, 120±50 ppbv, and 336.6±211 pptv in the marine air-mass, respectively. The enhancements in ozone, CO and NOy during high fire activity period are estimated to be 4-18%, 15-76% and 35-51% respectively. Higher CO/NOy ratio during winter indicate minimal influence of local activities.


About Speaker: She has completed her 5th year in ISRO ATCTM Project.



[40] Topic: Study of the aerosol characteristics over the central Himalayas

Speaker: Hema Joshi
Affiliation: ARIES
Date (yyyy-mm-dd): 2013-08-22
Time: 16:00hr
Venue: ARIES Auditorium

Abstract: Ground based observations of AOD, aerosols number concentrations and BC are made at Nainital (29.4 °N, 79.5 ºE, 1958 m amsl), a high altitude site in the central Himalayas, under ISRO-ARFI project. Surface observations of BC and AOD are also made at Pantnagar (29.0 °N, 79.5 ºE, 231 m amsl) under this project. Generally, AOD, aerosols number concentrations and BC shows a major peak during spring followed by autumn at Nainital. The BC mass concentration is found to be maximum (1.35 ± 0.74 µgm-3) in spring (Mar-May) and minimum during summer/monsoon (Jun-Aug) season (0.69 ± 0.52 µgm-3). Further BC is 0.90 ± 0.60 µgm-3 in autumn (Sep-Nov) and 1.00± 0.65 µgm-3 in winter (Dec-Feb) season at Nainital. The concentration weighted trajectories indicate that the regions nearby to the Nainital and other northern Indian regions having significant BC mass concentrations during spring time. It is found that the AOD as well as BC shows significant enhancement during the biomass period (April–May). The fine mode (0.3-1.0 µm) number concentration also increases abruptly during the fire-activity period. The enhanced BC and AOD (0.5 µm) due to biomass burning are estimated to be 1.80 µgm-3 (∼145%) and 0.3 (∼150%) respectively, which leads to additional atmospheric warming of 19 W m−2 and increases the lower atmospheric heating rate by 0.8 K day−1. The AOD as well as BC at Pantnagar are quite high as compared to that at Nainital. The diurnal variation of BC at Pantnagar is entirely different than at Nainital resulting in two peaks one in morning (0700-0900 hrs) and another in evening (1700 to 2100 hrs) hours. The average BC mass concentration at Pantnagar during winter seasons is found to be ~7.9±5.2 µgm-3 which is ~44% higher than the annual mean value. BC concentration gets reduced during the spring season and an average concentration of ~4.8±3.6 µgm-3 was observed in spring. The BC mass concentration during the summer/monsoon seasons reduces to a concentration of ~2.8±2.8 µgm-3 and is ~6.5±4.9 µgm-3 in autumn. The ground based observations at both the sites have been used in radiative estimations of aerosols and other properties extensively at both the sites.


About Speaker: She has completed her 5th year in ISRO ARFI Project.



[39] Topic: India’s Contribution to The Thirty Meter Telescope

Speaker: Dr. Ravinder S. Bhatia
Affiliation: TMT Associate Project Manager
Date (yyyy-mm-dd): 2013-08-12
Time: 11:00hr
Venue: ARIES Auditorium

Abstract: The Thirty Meter Telescope (TMT) represents the next generation of ground-based astronomical observatories. Driven by frontier science themes, TMT will offer 10 times the light-gathering power of the largest existing ground-based optical/near-infrared facilities, and will produce images 10 times more detailed than the Hubble Space Telescope. With this tremendous increase in power, TMT will deliver as yet unforeseen, groundbreaking discoveries about the Universe. In short, TMT will herald a new generation of telescopes and will serve its partner communities as a flagship research facility. TMT is an international partnership involving India, the USA, Canada, Japan, and China. Three main institutes constitute TMT-India: The Aryabhatta Research Institute for Observational Sciences (Nainital), the Indian Institute of Astrophysics (Bangalore) and the Inter-University Center for Astronomy and Astrophysics (Pune). The institutes are working closely with Indian industry to deliver key subsystems of the observatory, including polished segments of the main mirror, segment support assemblies, the onsite mirror re-coating facility, sensors and actuators for telescope controls, and software. These institutes also provide scientific input through their participation in the Scientific Advisory Committee. In this talk I will provide an overview of the scientific goals and technical architecture of the observatory. I will provide a status report on the construction activities, and describe the important scientific and technical contributions that are being made by India. I will also describe the challenges towards setting up the governance and management of an international partnership, and the ways in which Indian leadership is fostering an effective and collaborative working partnership.


About Speaker: Ravinder Bhatia gained his Batchelor’s degree in Aeronautics from Imperial College (1991), his Ph.D in Experimental Astrophysics and Aerospace Engineering from Queen Mary College (1998), and his Masters degree in International Relations from Cambridge University (2005). He has worked on international collaborations in technology development for over twenty years, in astronomy, Earth observation and oceanography. Previous assignments have included Project Systems Engineer for the Atacama Large Millimeter/subillimeter Array (ALMA), Senior Thermal/Cryogenics Engineer for the European Space Agency, Visiting Research Fellow at the UK National Oceanography Centre, and Senior Postdoctoral Scholar at Caltech.



[38] Topic: Analysis of Asian regional characteristics on greenhouse gaseous concentrations obtained by NIES flask sampling network

Speaker: Dr. Shohei Nomura
Affiliation: National Institute for Environmental Studies (NIES), Tsukuba, Japan
Date (yyyy-mm-dd): 2013-08-08
Time: 16:00hr
Venue: ARIES Auditorium

Abstract: This will be a short talk on the results from a networked based observations of greenshouse gases (GHGs).


About Speaker: Dr. Shohei Nomura is a scientist at NIES, Tsukuba, Japan



[37] Topic: Methane concentrations over Monsoon Asia as observed by satellite sensors: Signals of methane emission from rice cultivation

Speaker: Prof. Sachiko Hayashida
Affiliation: Nara Womens University, Nara, Japan
Date (yyyy-mm-dd): 2013-08-08
Time: 15:15hr
Venue: ARIES Auditorium

Abstract: We have analyzed the column-averaged CH4 concentration (xCH4) using scanning imaging absorption spectrometer for atmospheric chartography (SCIAMACHY) and compared the data with the bottom-up emission inventory datasets and other satellite-derived indices such as the land-surface water coverage (LSWC) and the normalized difference vegetation index (NDVI). The geographical distribution of high CH4 values corresponds to strong emissions from regions where rice is cultivated, as indicated in the inventory maps. The Pearson’s correlation coefficients (r) between xCH4 and the rice emission inventory data are observed to be greater than ~0.6 over typical rice fields, with outstanding r-values of ~0.8 in the Ganges Basin and the Sichuan Basin. This suggests that the emission of CH4 from rice cultivation mainly controls the seasonality of the CH4 concentration over such regions. The correlation between xCH4 and LSWC and NDVI are also as large as 0.6. In Southeast Asia, the r-values of xCH4 with bottom-up inventory data that includes all categories are not as high as those with the emission, as estimated from the rice category only. This is indicative of the relative importance of rice emissions among all other emission categories in Southeast Asia. In addition, I would like to introduce our research activities under the project "Characterization and Quantification of global methane emissions by utilizing GOSAT and other satellite sensors" sponsored by Ministry of Environment Japan.


About Speaker: Professor Hayashida contributed to the Improved Limb Atmospheric Spectrometer (ILAS) Science Team as a leader of validation for aerosol extinction measurements. She has also worked on Stratospheric Aerosol and Gas Experiment (SAGE) II and other satellite sensors. She investigated the composition of Polar Stratospheric Clouds (PSCs) and their effects on chemical processes related to polar ozone destruction, by utilizing ILAS data. Her group also developed a new simple scheme to construct synoptic maps of chemical species by combining trajectory mapping with a photochemical box model (Chemical Species Mapping on Trajectories). She received Horiuchi Award from Japan Meteorological Society in 2002 for her scientific achievements. Later she extended her study to tropospheric ozone, focusing on the spatiotemporal variation of tropospheric ozone distribution. She was a member of SPARC SSG from 2005 through 2008, and contributed to the joint scientific meeting of SPARC/IGAC in Kyoto, 2009 as one of the organizing committee members. Now, her most recent interest is methane emission from agriculture.



[36] Topic: Study of M6.5 Class Flare on 11th April 2013 and its Interplanetary Consequences

Speaker: Manjeet Kasotiya and Neha ingh
Affiliation: IIT Kanpur
Date (yyyy-mm-dd): 2013-07-25
Time: 15:30hr
Venue: Auditorium

Abstract: In this talk we will present the multi-wavelength analysis of M6.5 class flare occurred on 11 April,2013.This flare was observed at ARIES, Nainital.The flare was associated with full halo CMEs. We will discuss this event in the light of existing flare models.


About Speaker: B. Tech, undergraduate student of IIT Kanpur



[35] Topic: A multiwavelength polarimetric study towards the open cluster Stock 8

Speaker: Arunav Bordoloi
Affiliation: Project Student
Date (yyyy-mm-dd): 2013-07-12
Time: 15:30hr
Venue: Auditorium

Abstract: We broad-band (BV(RI)c) linear polarimetric observations of the stars located toward a young open cluster Stock 8. The mean polarisation and polarisation angles values are found to be 2.19±0.52%, 2.27±0.77%, 2.33±0.65%, 2.12±0.62% and 162±9 degree, 162±6 degree, 159±6 degree, 160±8 degree in the B, V, Rc, and Ic bands respectively. The peak mean polarisation observed in the R-band is consistent with the fact that the aligned dust grains towards Stock 8 are responsible for the origin of polarisation. The small dispersion in the polarisation angle might be due to the uniform alignment of dust grains and hence uniform magnetic field orientation. The mean value of maximum polarisation (Pmax) and the wavelength (λmax) at which maximum polarisation observed are found to be 2.23±0.46% and 0.58±0.10μm, respectively. The estimated mean value of λmax indicates that the average size of the dust grains towards the cluster is nearly similar to that for the general diffuse interstellar medium. Polarisation efficiency of the dust grains towards Stock 8 is similar to that observed towards NGC 1931 but less than that of NGC 1893. The observed less polarisation efficiency could be due to variations in the dust grain grain properties and/or their alignment efficiency along the line of sight towards Stock 8. We have used both optical color-color diagram and Stokes plane to find the cluster members.


About Speaker: The Speaker is currently enrolled in BS-MS degree (2nd year) of IISER Kolkata. He is a summer project student here under Dr A. K. Pandey. He is working from 17.05.2013 to 14.07.2013.



[34] Topic: Photometric Study of Eclipsing Binary System SS433

Speaker: Kishalay De
Affiliation: IISc, Bangalore
Date (yyyy-mm-dd): 2013-07-08
Time: 15:30hr
Venue: New Lecture Room

Abstract: Multi-wavelength photometric studies of SS 433 (also known as V1343 Aquilae) were carried out during the month of May, 2013 using the 104-cm Sampurnanand Optical Telescope at ARIES, Nainital, and their results are presented. The study aims to examine the periodicity in the obtained light curve for the object and correlate the results with previous studies. The present models for the system indicate that it is an eclipsing binary system with a B or A type supergiant and a compact object (possibly a low mass black hole) undergoing supercritical accretion from its companion star. Using data from the present photometric observations, the temperature of the secondary star appears to be around 9,000K - 11,000K, which is in agreement with typical temperatures for late B or early A type stars. Further, the radius estimated using typical luminosity values for B and A type supergiants is close to the expected radius for these stars. Using velocity data from previous spectroscopic studies and assuming an approximately circular orbit for the system, the binary separation turns out to be about 0.3 AU, with individual masses of 3.9 Msun for the compact object and 12.7 Msun for the companion star. Using Eggleton’s approximation for the radius of Roche Lobe for an object in a binary system, the secondary star appears to have filled its Roche Lobe completely. Further, using temperature extracted for the star surface, it is estimated that the radius of the accretion disk is likely to be equal to the equatorial radius of the Roche Lobe for the compact object. The circularization radius for the incoming stream of material is estimated to be around 5.7 Rsun.


About Speaker: VSP Student from IISc



[33] Topic: Constraints on Progenitors of Core-Collapse Supernovae

Speaker: RAYA DASTIDAR
Affiliation: IIT Hyderabad
Date (yyyy-mm-dd): 2013-07-05
Time: 15:00hr
Venue: Auditorium

Abstract: Observed properties of core-collapse SNe, such as light curve and spectra, are governed by the properties and environment of the progenitor star. Our objective has been to determine metallicity for a large sample of SNe at the location of explosion in their host galaxy and study the effect of metallicity on the properties of SNe types.


About Speaker: M.Sc. 1st year physics IIT Hyderabad



[32] Topic: Dynamical Modeling and Resonance Frequency Analysis of 3.6m Optical Telescope Pier

Speaker: Pradip Gatkine
Affiliation: IIT Bombay
Date (yyyy-mm-dd): 2013-07-05
Time: 14:30hr
Venue: Auditorium

Abstract: The Pier is a very important building block of any large optical telescope. It is very evident that there are several sources of strong vibrations all around the optical telescope. A large height makes it more vulnerable to low frequency oscillations, both as surface waves, as well as bulk oscillations. These vibrations may be transferred to the optical system, which mainly happens through the pier, since it is directly connected to the telescope. In order to avoid enhanced transfer of energy between pier and optical system, it is important to ensure that the resonance frequency of the pier and the telescope fixtures are fairly separated. Hence, the as-built structure of telescope pier was modeled and simulated using FEM analysis in Solidworks Package for finding the resonating modes. Also various test procedures were defined and on-site testing was done using 3C geophones as well as Piezoelectric sensors to validate the model and to closely observe the response of the pier. The main mode in low frequency regime was found to occur at approximately 23Hz by both the testing and simulations. Thus a few parameters about the telescope were fixed. Theoretical supports are also provided for observed modes. Also, a proof of concept was demonstrated for impulse response based resonance frequency determination. It was also demonstrated that a low-cost piezoelectric sensor based test-bench can be used for finding the resonating modes, compared to expensive 3C geophones.


About Speaker: Third Year Undergraduate student Department of Mechanical Engineering IIT Bombay



[31] Topic: Asteroseismology in South Africa and the impact of Kepler data on oscillating Eclipsing Algols (oEAs)

Speaker: Prof. Chris Engelbrecht
Affiliation: University of Johannesburg, South Africa
Date (yyyy-mm-dd): 2013-07-03
Time: 15:30hr
Venue: Auditorium

Abstract: The study of pulsating stars has a long and proud tradition in South Africa. The current research environment in this field in South Africa will be reviewed. In recent years, South African researchers have joined the asteroseismology consortium studying data from the Kepler space telescope. One prominent project, the study of oscillating eclipsing Algols using Kepler data, will also be reviewed.


About Speaker: Prof. Engelbrecht is working at the Department of Physics, University of Johannesburg, South Africa.



[30] Topic: A study of correlations between metallicity and opacity-driven pulsation in hot stars in the LMC

Speaker: Prof. Chris Engelbrecht
Affiliation: University of Johannesburg, South Africa
Date (yyyy-mm-dd): 2013-07-01
Time: 15:30hr
Venue: Auditorium

Abstract: Serious questions concerning our knowledge of stellar structure and evolution can be addressed through the asteroseismology of hot stars in the LMC and SMC. There is an apparent discrepancy between the theoretical prediction of pulsational instability in B stars and what w observe in nature. This discrepancy appears to relate to the way the metal content of hot stars affects their internal structure. The LMC and SMC are ideal testing grounds for our theories. A long-term project to study this problem at Sutherland in South Africa will be reviewed.


About Speaker: Prof. Engelbrecht is working at Department of Physics, University of Johannesburg, South Africa.



[29] Topic: STELLAR PULSATION: A NONLINEAR PERSPECTIVE

Speaker: Prof. M. K. Das
Affiliation: University of Delhi
Date (yyyy-mm-dd): 2013-07-05
Time: 15:30hr
Venue: Auditorium

Abstract: We have studied the temporal characteristics of different nonlinear stellar pulsation models in the nonlinear framework. In general the temporal behavior i.e., time series of amplitude variation are non-stationary and therefore the linear framework becomes inadequate for further characterization. Therefore, we have used wavelet analysis to investigate their characteristics in the time-frequency domain. Further the time series obtained in most of these model suggests period doubling and chaotic behavior for certain control parameters, in the phase space. As usually only one observational parameter is measured in a given setting, it is used to reconstruct an attractor in the phase space using phase space reconstruction method. Further characterization of the attractor and hence the time series ,obtained for various models, have been made using the recurrence quantification analysis (RQA).


About Speaker: Prof. Das is presently associated with Institute of Informatics & Communication University of Delhi South Campus.



[28] Topic: Cometary dust - a probe for early solar nebula

Speaker: Prof. U. C. Joshi
Affiliation: PRL, Ahmedabad
Date (yyyy-mm-dd): 2013-05-23
Time: 15:30hr
Venue: Auditorium

Abstract: The physical and optical properties of cometary dust grains are of great interest at least for two reasons: i) these grains are responsible for much of the light scattered from cometary coma and dust tail; hence grain optics influences the basic appearances of comets; ii) the grains may be unprocessed relics from the time of formation of the solar system or before, hence study of cometary grains is very important to investigate physical conditions that exited in the beginning of the formation of solar system. This information is imprinted in the cometary dust grains. There are several ways that the cometary dust can be studied - in situ measurements using space experiments, ground based observations etc. As space based experiments are expensive and comets show differing properties, ground based studies of comets are very relevant. Photopolarimetry of the coma of comets serves as an important tool to study cometary dust. The talk will focus on a brief overview of comet study and its contribution to basic sciences. Apart from this, we have studied several comets using polarization and photometric methods. Characteristics of the cometary grains as revealed from photometric and polarimetric observations at low phase angle along with the opposition effects based on the study of comet C/2007 N3 (Lulin) by us in recent times will be discussed.


About Speaker: Prof. U. C. Joshi is a retired professor in Astronomy and Astrophysics Division of PRL, Ahmedabad. At present his is visiting faculty in the same place.



[27] Topic: Development of Uttrakhand: Dream Big, Start Small

Speaker: Prof. S K Joshi
Affiliation: Prof. Emeritus, NPL Delhi
Date (yyyy-mm-dd): 2013-05-24
Time: 15:30hr
Venue: New Lecture Room

Abstract: .


About Speaker: Prof. S K Joshi is presently Prof. Emeritus at NPL Delhi. He was former Director of NPL and former Director General of CSIR.



[23] Topic: Study of Ozone and other Trace Gases Distribution in the Lower Atmosphere

Speaker: Narendra Ojha
Affiliation: ARIES, 6th year student
Date (yyyy-mm-dd): 2013-05-16
Time: 15:30hr
Venue: ARIES New Lecture room

Abstract: Tropospheric ozone plays a key role in the air quality, atmospheric chemistry and climate change; however, its budget and its role in these processes are not well understood mainly due to lack of sufficient measurements. Satellite and model studies revealed elevated levels of ozone and other pollutants over the Indo-Gangetic Plain (IGP) in the Northern India; however, in lack of in situ measurements, the understanding of underlying physical, chemical and dynamical processes is very limited. Moreover, since the climatic impacts of tropospheric ozone are dependent upon its vertical distribution, the systematic and long-term measurements of ozone distribution are needed. In view of this, weekly balloon flights have been conducted to measure vertical distribution of ozone (EN-SCI 2ZV7 ECC Ozonesonde) and meteorological parameters (iMet-1-RSB 403 MHz GPS Radiosonde) from a high altitude site Nainital (79.5oE, 29.4oN, 1958 m amsl) in the central Himalayas since January 2011. Additionally, surface ozone measurements have been made at two sites, Pantnagar (79.5oE, 29.0oN, 231 m amsl) and Dehradun (78.1oE, 30.3oN, 640 m amsl), in the IGP region since 2009. Weekly air samples are also collected at Nainital for analysis of CO and greenhouse gases CO2 and CH4 in collaboration with NIES, Japan. Chemical box model (NCAR Master Mechanism), a regional chemistry transport model (WRF-Chem) and data from global models (MATCH-MPIC and MOZART) are used to understand the observed variabilities. Surface ozone at Pantnagar site in the IGP shows daytime build-up with levels sometimes as high as 100 ppbv. Ozone seasonal variations exhibit highest levels during spring (39.3±18.9 ppbv in May) and lower levels in summer-monsoon (16.8±8.9 ppbv in August) and winter (10.8±12.1 ppbv in January). This ozone seasonality is in agreement with the meteorological parameters and satellite observations of tropospheric NO2 and CO (681 hPa). A global model (MATCH-MPIC) captures the seasonality but overestimates the ozone levels. Model simulated daytime H2O2/HNO3 values are higher indicating NOx-limited chemistry over this region. Box model simulations are used to corroborate this and to estimate integrated net ozone production in a day (72.9 ppbv). Strong positive correlation (r2 = 0.96 in May) between the daytime ozone at IGP and nearby Himalayan site suggests transport of pollution from IGP to the cleaner Himalayas via boundary layer evolution. Estimated 3-monthly AOT40 index, using the observed ozone data, indicates threat for vegetations in the IGP region. Balloon-borne observations revealed large variability in the vertical distribution of ozone and meteorological parameters. Tropopause pressure from radiosonde observations agrees with the satellite (AIRS and TES) and model results, but shows dramatic variability (150-250 hPa) during winter and early spring. Lower tropospheric (2-6 km amsl) ozone shows a prominent seasonality with spring maxima (~70-110 ppbv in May) and summer-monsoon minima (~20-50 ppbv), which is consistent with the surface observations. Springtime ozone profiles are classified using MODIS fire counts, and ozone levels during high fire activity periods are observed to be higher by 19.9±4.6 ppbv in 2-4 km altitude range, as compared with low fire activity period. Signature of ozone downward transport, noticed during winter, is corroborated with observed reduction in relative humidity (radiosonde and AIRS satellite) and enhancement in potential vorticity (WRF). However, model simulated ozone profiles discern enhancements at lower altitudes than observations. A comparison of ozonesonde observations with collocated satellite (TES) retrievals shows reasonable agreement. Tropospheric column ozone (TCO) from the ozonesonde observations show a typical seasonality comprising of spring maxima (47.2±9.8 DU) and winter minima (30.4±10.1 DU). The long-term data of CO2, CH4 and CO during September 2006-December 2011, obtained from the sample analysis, has been analyzed for the seasonal variations and long-term trends. CO2 shows a prominent seasonality over Nainital with the spring maximum (395.9±5.9 ppmv in May) and post-monsoon/autumn minimum (374.4±5.8 ppmv in October). CO2 seasonal cycle at Nainital is similar to that at Mauna Loa, however, the seasonal amplitude in CO2 is much larger at Nainital (~21.5 ppmv) as compared with the Mauna Loa (~6.5 ppmv). Long-term trends in CO2, CH4 and CO have been investigated by deseasonalizing the time series and a linear regression fit. The estimated trend in CO2 over Nainital (1.88 ppmv per year) is consistent with the trends over Mauna Loa (1.60 to 2.43 ppmv per year) and global marine observations (1.64 to 2.40 ppmv per year). CH4 levels discern a small positive trend of 4 ppbv per year, while, CO levels show a negative trend of 7.3 ppbv per year.


About Speaker: Narendra is the 6th year student in ARIES working under Dr. Manish Naja.



[17] Topic: Latitudinal variation of Aerosol Properties from Indo Gangetic Plains to central Himalayan foothills

Speaker: Dr U C Dumka
Affiliation: ARIES
Date (yyyy-mm-dd): 2013-05-14
Time: 15:30hr
Venue: ARIES Lecture Hall

Abstract: Latitudinal spatial variations in aerosol optical properties are analysed over the Indo-Gangetic Plains (IGP) of northern India to a highland location in the central Himalayas during pre-monsoon (April to June) of the 2008 and 2009. Measurements of aerosol optical depth (AOD) were performed using ground based sun photometers at four sites in different aerosol environments. The AOD values increase from Kanpur (a major industrial city in central IGP) to Nainital. Further, aerosol size varies spatially with the dominance of coarse mode aerosols at Kanpur (due mainly to mineral dust transport) compared to fine mode dominated aerosols at Nainital. The spectral variation of single scattering albedo suggests the dominance of dust from IGP to Himalayan foothills (Pantnagar) during the pre-monsoon. More absorbing aerosols are retrieved at Pantnagar than Kanpur. The short wave aerosol radiative forcing (ARF) is estimated and the optical properties of aerosols (e.g. AOD, SSA, asymmetry parameter) are calculated and will be discussed.


About Speaker: ARIES



[16] Topic: Origin of Macrospicule and Jet in Polar Corona by A Small-scale Kinked Flux-Tube

Speaker: P. Kayshap
Affiliation: ARIES, Nainital
Date (yyyy-mm-dd): 2013-05-28
Time: 15:30hr
Venue: New Auditorium

Abstract: We report first observations of a small scale flux-tube that undergoes kinking and triggers the macrospicule and a jet on November 11, 2010 in the north polar corona. The small-scale flux-tube emerged well before the triggering of macrospicule and as the time progresses the two opposite halves of this omega shaped flux-tube bent transversely and approached towards each other. After 2 minutes, the two approaching halves of the kinked flux-tube touch each-other and internal reconnection as well as energy release takes place at the adjoining location and a macrospicule was launched which goes upto a height of ~12 Mm. Plasma starts moving horizontally as well as vertically upward along with the onset of macrospicule and thereafter converts into a large-scale jet in which the core denser material reaches upto 40 Mm with a projected speed of 95 km/s in its fast rising phase. We perform 2-D numerical simulation by considering the VAL-C initial atmospheric conditions to understand the physical scenario of the observed macrospicule and associated jet. The simulation results show that reconnection generated velocity pulse in the lower solar atmosphere steepens into slow shock and the cool plasma is driven behind it in form of macrospicule. The horizontal surface waves also appeared with the shock fronts at different heights, which most likely drove and spread the large-scale jet associated with the macrospicule.


About Speaker: P. Kayshap is working as a Senior Research Fellow at ARIES. He is pursuing the solar research on the study of trigger mechanisms of various kinds of transients and plasma dynamics in the solar atmosphere, as well as their MHD aspects to understand physical significance.



[15] Topic: PHOTOMETRIC STUDIES OF OPEN STAR CLUSTER Rup32

Speaker: Mr. Sidhant Guliani
Affiliation: Guru Gobind Singh Indraprastha Univeristy, New Delhi
Date (yyyy-mm-dd): 2013-04-29
Time: 14:45hr
Venue: ARIES New Lecture room

Abstract: .


About Speaker: Project Student



[13] Topic: Study of Chemically Peculiar Red Giants

Speaker: Bharat Yerra
Affiliation: ARIES
Date (yyyy-mm-dd): 2013-04-26
Time: 15:30hr
Venue: ARIES New Lecture room

Abstract: Chemically peculiar red giants, Li-rich K giants and Weak G-band (WGB) stars, are rare class of cool luminous stars whose spctra show strong Li resonance line at 6707 Ang and very weak or absent G-bands of the CH~A$^{2}Delta$ - X$^{2}Pi$ system at 4300 AA. Some of these stars are also associated with other peculiarities like: Infrared excess, rapid rotation, activity, and binarity. The origin of such anomalies in these class of stars are not well understood. To understand the underlying physical process for such anomalies, and to check the relation between their peculiarities, we have initiated a systematic study of Li-rich K giants and WGB stars. In this talk, I will discuss the properties of Li-rich K giants and WGB stars, and the results obtained from various observations.


About Speaker: Bharat is a postdoc in ARIES for the last one year, and has applied for two months extension.



[12] Topic: Radiatively and thermally driven jets from dissipative accretion discs

Speaker: Rajiv Kumar
Affiliation: ARIES
Date (yyyy-mm-dd): 2013-04-30
Time: 15:30hr
Venue: ARIES New Lecture room

Abstract: As the accreting matter comes close to a black hole, it may form a shock due to centrifugal barrier and may eject the rotating matter along the axis in the form of jets. And the post-shock region puffs up due to shock heating and forms a torus like structure. These post-shock hot electrons emit hard X-ray photons by inverse Comptonization of pre and post-shock soft photons. Radiations from accretion disc can accelerate the outflowing matter. We self consistently compute shock driven bipolar outflows, which are accelerated by accretion disc photons. Although we have earlier studied the issue of radiative acceleration of jets, and formation of jets from shocked accretion disc, but the two have never been connected. We vary all possible disc parameters to see how they affect the jet formation and acceleration. For some extreme parameters the jet terminal speed is found to be as high as 50% the speed of light, although, in most cases the terminal speed for such jets are around 10 to 30 % of the speed of light.


About Speaker: Rajiv is a 4th year student in ARIES. He works in theoretical astrophysics, especially on generation of bipolar jets from accretion discs.



[10] Topic: HR diagram and Sahas Theory of Thermal ionization

Speaker: Prof. D. C. Srivastava
Affiliation: DDUGU
Date (yyyy-mm-dd): 2013-04-16
Time: 15:30hr
Venue: New Lecture Hall

Abstract: Application of Sahas Theory of Thermal Ionisation to Specral Types and HR diagram will be discussed. A discussion of Spectral Classification and Sahas Theory will also be presented in the Historical perspectives.


About Speaker: Senior Professor of the Physics Department of Gorakhpur University. Served as its HOD till recently.



[9] Topic: Activity in A-type stars

Speaker: Prof. Luis Balona
Affiliation: South African Astronomical Observatory (SAAO), South Africa
Date (yyyy-mm-dd): 2013-03-26
Time: 15:30hr
Venue: Auditorium

Abstract: Kepler photometry shows that most non-pulsating A-type stars vary with periodstypical of the expected rotation periods. The periodogram is simple and usually consists of a peak and its harmonic with amplitudes typically smaller than 50 ppm. We presume that the variation is rotational modulation caused by spots or some other co-rotating obscuration. This is supported by the distribution of equatorial velocities derived from the photometric periods. From the broadening of the peaks in the periodogram, we estimate that differential rotation in A-type stars is very similar to that in the Sun. Flares on A-type stars have been recently discovered in Kepler data. We show that such flares cannot be attributed to a late-type companion but must originate on the A star itself or an interaction between the A star and a close companion. We also discuss activity in B-type stars and argue that Be stars, in particular, are magnetically active. We present a simple model which explains all major characteristics of Be stars.


About Speaker: http://www.saao.ac.za/~lab/



[8] Topic: Oxidation capacity influenced by Convection

Speaker: Dr. Hartwig Harder
Affiliation: Max Planck Institute for Chemistry
Date (yyyy-mm-dd): 2013-03-11
Time: 15:30hr
Venue: Auditorium

Abstract: Self-cleaning processes in the atmosphere occur via oxidation processes, dominated by OH radicals. OH measurements taken in different environments, from remote marine locations, tropical and boreal forests as well as over Europe, and at different altitudes, illustrate our current understanding of HOx chemistry. While in clean air measured OH matches expectations, more polluted air, and also air with biogenic emissions, often shows enhancements of OH that indicate unknown additional processes. Convection can transport such air into higher altitudes, significantly alterating the oxidative chemistry in the upper troposphere.


About Speaker: Group Leader and group hompage http://www.mpic.de/en/research/atmospheric-chemistry/group-harder.html



[7] Topic: Thirty Meter Telescope Project Overview

Speaker: Dr. Eric Williams
Affiliation: TMT, CALTECH
Date (yyyy-mm-dd): 2013-03-01
Time: 15:30hr
Venue: Auditorium

Abstract: Thirty Meter Telescope Project Overview


About Speaker: Eric Williams is TMT Optics Group Leader responsible for the design, fabrication, testing and integration of the telescope optics. Eric has been involved in the TMT project for 8 years. Prior to joining TMT, Eric worked in the U.S. Aerospace Industry on a wide range of projects.



[5] Topic: The SALT Instrumentation Suite

Speaker: David Buckley
Affiliation: South African Astonomical Observatory
Date (yyyy-mm-dd): 2013-03-12
Time: 15:30hr
Venue: Auditorium

Abstract: Construction of the 10-m Southern African Large Telescope (SALT) was completed in 2005 at a relatively modest cost of $20M and in just 6 years. Following a rather protracted commissioning and science verification phase, during which two major problems were discovered and corrected, briefly reviewed here, it entered full science operations in 2011. This talk will discuss the design and construction of SALT and its First Generation instruments, SALTICAM and the Robert Stobie Spectrograph, and highlight their capabilities, particularly some of the niche observing modes, and will present some examples of initial science results. New SALT instrumentation currently under construction, including the High Resolution Spectrograph and the near IR extension to the RSS, will also be discussed.


About Speaker: SALT Science Director Webpage: http://www.salt.ac.za/about/people-partners/operations-team/david-buckley/



[4] Topic: On the Processes Influencing the Vertical Distribution of Ozone over the central Himalayas

Speaker: Narendra Ojha
Affiliation: ARIES Nainital
Date (yyyy-mm-dd): 2013-02-19
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: Balloon-borne measurements of ozone vertical distribution and meteorological parameters are presented for a complete seasonal cycle (2011) for the first time, from a high altitude site Nainital (79.5oE, 29.4oN, 1958 m amsl) in the central Himalayas. Balloons, carrying an ozonesonde (EN-SCI 2ZV7 ECC) and a radiosonde (iMet-1-RSB 403 MHz GPS) were launched with a frequency of 3-4 flights per month which resulted in a collection of total 48 profiles during 2011. Maiden observations revealed large variabilities in the ozone distribution and meteorological parameters. Tropopause pressure is estimated to be ~100 hPa from the radiosonde observations and is in agreement with the satellite (AIRS and TES) and model (WRF) results but shows dramatic variability (150-250 hPa) during winter and early spring. Relative humidity in the lower troposphere is highest (80-100%) during summer and is attributed to the arrival of monsoon. Occasionally observed very high wind speed (~40 to 80 m/s) in middle-upper troposphere, particularly during winter, is suggested to be associated with the subtropical jets. Lower tropospheric (2-6 km amsl) ozone shows a prominent seasonality with highest levels during spring (~70-110 ppbv in May) and lowest levels during summer-monsoon (~20-50 ppbv), which is consistent with the surface observations and satellite data over this region. However, ozone seasonality is less pronounced in the middle-upper troposphere. A prominent feature of secondary ozone peaks have been observed on several occasions in the middle-upper troposphere more frequently during spring. Springtime ozone profiles are classified into high and low fire activity periods using MODIS fire counts and influence of biomass burning is estimated to be 19.9±4.6 ppbv in 2 to 4 km altitude range. Regional photochemistry is suggested to be the key process during spring with a significant contribution from the north-Indian biomass burning. Dynamical processes including advection and stratospheric intrusions play key roles except during summer-monsoon. Ozonesonde profiles with the TES operator are shown to be in good agreement with the collocated satellite (TES) retrievals. Estimated tropospheric column ozone show differences between the ozonesonde and TES during winter and is shown to be associated with the tropopause variability. These observations form invaluable datasets for the validation of satellite and model results, which is severely lacking over this region so far.


About Speaker: Mr. Narendra Ojha is Senior Research Fellow at ARIES working on distribution of Trace Gases under guidance of Dr. Manish Naja.



[3] Topic: Star formation in Wolf-Rayet galaxy Mrk~996 : Devasthal Fast Optical Telescope observations

Speaker: Mr. Sumit Jaiswal
Affiliation: ARIES
Date (yyyy-mm-dd): 2013-02-05
Time: 15:30hr
Venue: Audotorium

Abstract: The Halpha observation of the Wolf-Rayet (WR) galaxy Mrk~996 using the newly installed 1.3 meter Devasthal Fast Optical Telescope (DFOT) are presented. Mrk~996 is a well studied galaxy, however, Ha flux and star formation rate (SFR) in the galaxy are poorly constrained by different investigators over a range of 0.2 - 3.8 ~M_sun/yr. It is classified as nE, blue compact dwarf galaxy with extremely dense gas in the core. The H-alpha analysis presented here is corrected for line contamination, Milky-way extinction, internal extinction, stellar continuum and the underlying stellar absorption. The age of the star-burst is estimated as $8 Myr. It is also noticed that the ionized gas as traced by the Ha emission is in a disk shape, which is misaligned with respect to the old stellar disk. This misalignment is indicative of a recent tidal interaction in the galaxy. We believe that the galaxy-galaxy tidal interaction is the main cause of the WR phase in Mrk~996.


About Speaker: Mr. Sumit Jaiswal work on Wolf-Ray Galaxy. He at presnt is in 4th year of his Ph.D, whic he is pursuing with Dr. A. Omar.



[2] Topic: Magnetic Field Structure around Dense Molecular Cores with Very Low Luminosity Objects .

Speaker: Ms. Archana Soam
Affiliation: ARIES
Date (yyyy-mm-dd): 2013-02-12
Time: 15:30hr
Venue: Audotorium

Abstract: We present the results of polarization measurements of stars projected on four dense cores that are found to harbor Very Low Luminosity Objects detected by the Spitzer Space telescope. The observed dense cores are IRAM 04191+1522, L1521F, L673-7 and L1014. In IRAM 04191+1522, the separation between the magnetic field direction inferred from the optical polarization and the outflow direction is 84 degree while the separation between the magnetic field inferred from the submillimeter polarization and the outflow direction is ~ 3 degree. IRAM 04191+1522 exhibits a wind-blown morphology conspicuous in the WISE 12μm image. The direction of the maximum velocity gradient in IRAM 04191+1522 is found to be in a direction roughly perpendicular to the direction of the magnetic field inferred from the submillimeter observations. In L1521F the offset between the outflow direction and the magnetic field from our optical polarization is found to be ~ 48 degree. In L673-7 dense core, the magnetic field lines are found to be more chaotic with a slight hint of the outflow being parallel to the field towards the northern parts of the cloud. The offset between the magnetic field orientation and the outflow is found to be ~ 8 degree. In L1014, the separation between the magnetic field orientation and the outflow is found to be ~ 15 degree. The minor axis of the cloud is almost parallel to the magnetic field orientation at the periphery of the cloud.


About Speaker: Archana is ARIES 4ye student. Her Ph. D is on Polarimetry carrying under the supervision of Dr. Maheshwar Gopinathan.