A5018029802- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Galaxies: Formation, Evolution, Phenomena
- Adaptive optics and wavefront sensing
- Astro and Planetary Science
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- History and Developments in Astronomy
- Space Exploration and Technology
- Photocathodes and Microchannel Plates
- Calibration and Measurement Techniques
- CCD and CMOS Imaging Sensors
- Solar and Space Plasma Dynamics
- Spectroscopy and Laser Applications
- Distributed and Parallel Computing Systems
- Impact of Light on Environment and Health
- Atmospheric Ozone and Climate
- Particle Accelerators and Free-Electron Lasers
- Spacecraft and Cryogenic Technologies
- Infrared Target Detection Methodologies
- Leaf Properties and Growth Measurement
- Astrophysics and Cosmic Phenomena
- Agronomic Practices and Intercropping Systems
Indian Institute of Astrophysics
2015-2024
Vellore Institute of Technology University
2016
University of California, Irvine
2016
University of California, San Diego
2016
TMT Observatory
2016
University of Calicut
2013
Indian Institute of Technology Madras
2011
European Southern Observatory
2010
Institut de Planétologie et d'Astrophysique de Grenoble
2010
Osservatorio Astronomico di Padova
2010
Abstract The Ultra-Violet Imaging Telescope (UVIT) is one of the payloads in ASTROSAT, first Indian Space Observatory. UVIT instrument has two 375 mm telescopes: for far-ultraviolet (FUV) channel (1300–1800 Å), and other near-ultraviolet (NUV) (2000–3000 Å) visible (VIS) (3200–5500 Å). primarily designed simultaneous imaging ultraviolet channels with spatial resolution better than 1.″8, along provisions slit-less spectroscopy NUV FUV channels. results in-orbit calibrations are presented this paper.
ASTROSAT is India's first astronomy satellite that will carry an array of instruments capable simultaneous observations in a broad range wavelengths: from the visible, near ultraviolet (NUV), far-UV (FUV), soft X-rays to hard X-rays. There be five principal scientific payloads aboard satellite: (i) Soft X-ray Telescope (SXT), (ii) three Large Area Xenon Proportional Counters (LAXPCs), (iii) Cadmium-Zinc-Telluride Imager (CZTI), (iv) two Ultra-Violet Imaging Telescopes (UVITs) one for visible...
Results of the initial calibration Ultra-Violet Imaging Telescope (UVIT) were reported earlier by Tandon et al. (2017). The results based on ground as well first observations in orbit. Some additional data from and more in-orbit have been used to improve results. In particular, extensive new obtain (a) photometric which includes (i) zero-points (ii) flat fields (iii) saturation, (b) sensitivity variations (c) spectral for near Ultra Violet (NUV; 2000 - 3000 Angstroms) far (FUV; 1300 1800...
The three-dimensional structure of the inner Small Magellanic Cloud (SMC) is investigated using red clump (RC) stars and RR Lyrae (RRLS), which represent intermediate-age old stellar populations a galaxy. V- I-band photometric data from OGLE III catalog are used for our study. mean dereddened I0 magnitude RC RRLS to study relative positions different regions in SMC with respect distance. This shows that northeastern part closer us. line-of-sight depth (front back distance) across estimated...
Using imaging that shows four magnitudes of main sequence stars, we have discovered the Galactic globular cluster NGC 1851 is surrounded by a halo visible from tidal radius 700 arcsec (41 pc) to more than 4500 (>250 pc). This symmetric and falls in density as power law $r^{-1.24}$. It contains approximately 0.1% dynamical mass 1851. There no evidence for tails. Current models evolution do not explain this feature, although simulations influences on dwarf spheroidal galaxies qualitatively...
[abridged] We describe the first results from NOAO Outer Limits Survey. The survey consists of deep images 55 0.6x0.6 degree fields at distances up to 20 degrees LMC/SMC, and 10 controls. probe outer structure Clouds, Magellanic Stream, Leading Arm, wake new LMC orbit. Images were taken in 5 filters on CTIO Blanco 4-m Mosaic2 camera, with calibration 0.9-m. CRI reach depths below oldest LMC/SMC main sequence (MS) turnoffs, yielding probes combined ability measure stellar ages metallicities....
<i>Context. <i/>A systematic estimation of the line sight depth in disk and bar regions Large Small Magellanic Clouds (LMC SMC) using red clump stars is presented.<i>Aims. <i/>We used from photometric data Optical Gravitational Lensing Experiment (OGLE II) survey Cloud Photometric Survey (MCPS) for both to estimate depth. <i>Methods. <i/>The observed dispersion magnitude colour distribution depth, after correcting population effects, internal reddening within errors.<i>Results. due ranges...
We have estimated a metallicity map of the Large Magellanic Cloud (LMC) using Photometric Survey (MCPS) and Optical Gravitational Lensing Experiment (OGLE III) photometric data. This is first its kind up to radius 4 - 5 degrees, derived data calibrated spectroscopic Red Giant Branch (RGB) stars. identify RGB in V, (V$-$I) colour magnitude diagrams small subregions varying sizes both sets. use slope as an indicator average subregion, calibrate for field cluster red giants selected subregions....
We present results from the largest Ca ii triplet line metallicity study of Small Magellanic Cloud (SMC) field red giant stars to date, involving 3037 objects spread across approximately 37.5 deg2, centred on this galaxy. find a median [Fe/H] = −0.99 ± 0.01, with clear evidence for an abundance gradient −0.075 0.011 dex deg−1 over inner 5°. interpret be result increasing fraction young decreasing galactocentric radius, coupled uniform global age–metallicity relation. also demonstrate that...
We present results from an extensive spectroscopic survey of field stars in the Small Magellanic Cloud (SMC). 3037 sources, predominantly first-ascent red giants, spread across roughly 37.5 sq. deg, are analysed. The line sight velocity is dominated by projection orbital motion SMC around LMC/Milky Way. residuals inconsistent with both a non-rotating spheroid and nearly face on disk system. current sample previous stellar HI kinematics can be reconciled rotating models nodes position angle,...
Jellyfish are cluster galaxies that experience strong ram-pressure effects strip their gas. Their Hα images reveal ionized gas tails up to 100 kpc, which could be hosting ongoing star formation. Here, we report the ultraviolet (UV) imaging observation of jellyfish galaxy JO201 obtained at a spatial resolution ∼1.3 kpc. The intense burst formation happening in tentacles is focus this study. 'UV-brightest galaxy' Abell 85 (z ∼ 0.056) with knots and streams UV. We identify star-forming both...
NGC 7789 is a $\sim$1.6 Gyr old, populous open cluster located at $\sim$2000 pc. We characterize the blue straggler stars (BSS) of this using Ultraviolet (UV) data from UVIT/AstroSat. present spectral energy distributions (SED) 15 BSS candidates constructed multi-wavelength ranging UV to IR wavelengths. In 8 candidates, single temperature SED found be satisfactory. discover hot companions in 5 candidates. The with Teff $\sim$11750-15500 K, R $\sim$0.069-0.242 R$_{\odot}$, and L...
We modeled the kinematics of Small Magellanic Cloud (SMC) by analyzing proper motion (PM) from Gaia DR3 nine different stellar populations, which include young main sequence (MS) stars (< 2 Gyr), red giant branch stars, clump giants with line-of-sight velocities, and three groups star clusters. This analysis was carried out using a robust Markov Chain Monte Carlo method to derive up 7 kinematic parameters. trace evolution non-rotating flattened elliptical system as mapped old population...
Abstract We model the kinematics of Small Magellanic Cloud (SMC) by analyzing proper motions (PMs) from Gaia DR3 nine different stellar populations, including young main-sequence (MS) stars (<2 Gyr), red giant branch stars, clump giants with line-of-sight velocities, and three groups star clusters. This analysis is carried out using a robust Markov Chain Monte Carlo method, to derive up seven kinematic parameters. trace evolution nonrotating flattened elliptical system, as mapped old...
We reconstructed the star formation histories of seven massive (M_ ⋆ ≳ 10^ early-type galaxies (ETGs) in Virgo cluster by analysing their spatially resolved stellar population (SP) properties including ultraviolet (UV) and Hα emission. As part Environmental Survey Tracing Ionised Gas Emission (VESTIGE), we used images to select ETGs that show no signs ongoing formation. combined VESTIGE with from Astrosat/UVIT, GALEX, CFHT/MegaCam Next Generation Cluster (NGVS) analyse radial spectral energy...
view Abstract Citations (103) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Steps toward Determination of the Size and Structure Broad-Line Region in Active Galactic Nuclei. VI. Variability NGC 3783 from Ground-based Data Stirpe, G. M. ; Winge, C. Altieri, B. Alloin, D. Aguero, E. L. Anupama, Ashley, R. Bertram, Calderon, J. H. Catchpole, Corradi, Covino, Dottori, A. Feast, W. Ghosh, K. Hutton, Gil Glass, I. S. Grebel, Jorda, Koen, Laney,...
We have created an estimated metallicity map of the Small Magellanic Cloud (SMC) using Photometric Survey (MCPS) and Optical Gravitational Lensing Experiment (OGLE III) photometric data. This is a first its kind up to radius $\sim$ 2.5$^{\circ}$. identify RGB in V, (V$-$I) colour magnitude diagrams small subregions varying sizes both data sets. use slope as indicator average subregion, calibrate available spectroscopic for selected subregions. The SMC found be [Fe/H] = $-$0.94 dex ($σ$[Fe/H]...
We report evidence for star formation quenching in the central 8.6 kpc region of jellyfish galaxy JO201 which hosts an active galactic nucleus, while undergoing strong ram pressure stripping. The ultraviolet imaging data disk reveal a with reduced flux around center and horse shoe shaped enhanced outer disk. characterization ionization regions based on emission line diagnostic diagrams shows that seen is within AGN-dominated area. CO J$_{2-1}$ map reveals cavity region. image at redder...
A detailed study of the ultraviolet (UV) bright stars in old open star cluster, M67 is presented based on far-UV observations using {\it Ultra Violet Imaging Telescope} ({\it UVIT}) ASTROSAT}. The UV and UV-optical colour-magnitude diagrams (CMDs) along with overlaid isochrones are for member stars, which include blue straggler (BSSs), triple systems, white dwarfs (WDs) spectroscopic binaries (SB). CMDs suggest presence excess flux many members, could be extrinsic or intrinsic to them. We...
Abstract The old open cluster M67, populated with blue straggler stars (BSSs), is a well-known test bed to study the BSS formation pathways. Here, we report first direct detection of white dwarf (WD) companion in using far-UV images from Ultra-Violet Imaging telescope on ASTROSAT . Near-simultaneous observations three bands combined Galaxy Evolution Explorer , International Ultraviolet and ground- space-based photometric data covering 0.14–11.5 μ m range for WOCS1007 were found require...
ABSTRACT Blue straggler stars (BSSs) are the most massive in a cluster formed via binary or higher order stellar interactions. Though exact nature of such formation scenarios is difficult to pin down, we provide observational constraints on different possible mechanism. In this quest, first produce catalogue BSSs using Gaia DR2 data. Among 670 clusters older than 300 Myr, identified 868 228 and 500 BSS candidates 208 clusters. general, all 1 Gyr 1000 M⊙ have BSSs. The average number...
ABSTRACT We present a detailed view of cluster formation (CF) to trace the evolution and interaction history Magellanic Clouds (MCs) in last 3.5 Gyr. Using Gaia DR3 data, we parametrized 1710 280 star clusters Large Cloud (LMC) Small (SMC), where 847 113 are newly characterized outer LMC SMC, respectively. estimated age–extinction–metallicity–distance parameters using an automated fitting colour–magnitude diagram (CMD) after field removal, followed by Markov chain Monte Carlo technique....
<i>Aims. <i/>We used the red clump stars from <i>VI<i/> photometric data of Optical Gravitational Lensing Experiment (OGLE III) survey and Magellanic Cloud Photometric Survey (MCPS) to estimate structural parameters LMC disk, such as inclination, <i>i<i/> position angle line nodes (PA<sub>lon<sub/>), <i>ϕ<i/>.<i>Methods. <i/>The observed disk region is divided into sub-regions. The dereddened peak <i>I<i/> magnitude in each sub-region obtain relative distances hence <i>z<i/> coordinate. RA...
Emission-line stars in young open clusters are identified to study their properties, as a function of age, spectral type and evolutionary state. 207 star were observed using the slitless spectroscopy method 157 emission 42 clusters. We have found 54 new emission-line 24 clusters, out which 19 house for first time. About 20 per cent harbour stars. The fraction housing is maximum both 0–10 20–30 Myr age bin (∼40 each). Most our survey belong Classical Be class (∼92 cent) while few Herbig (∼6...