V. Bhalerao
A5024878038- Gamma-ray bursts and supernovae
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Pulsars and Gravitational Waves Research
- Astrophysical Phenomena and Observations
- SAS software applications and methods
- Astrophysics and Cosmic Phenomena
- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Adaptive optics and wavefront sensing
- Particle Detector Development and Performance
- Nuclear Physics and Applications
- High-pressure geophysics and materials
- Magnetic confinement fusion research
- Geophysics and Gravity Measurements
- Planetary Science and Exploration
- Advanced X-ray and CT Imaging
- Particle Accelerators and Free-Electron Lasers
- Advanced Semiconductor Detectors and Materials
- Particle accelerators and beam dynamics
- Superconducting Materials and Applications
- Isotope Analysis in Ecology
- Calibration and Measurement Techniques
- Solar and Space Plasma Dynamics
- Inertial Sensor and Navigation
Indian Institute of Technology Bombay
2005-2025
Aryabhatta Research Institute of Observational Sciences
2021
National Centre for Radio Astrophysics
2018
Tata Institute of Fundamental Research
2018
Inter-University Centre for Astronomy and Astrophysics
2013-2017
International University of the Caribbean
2015
California Institute of Technology
2010-2014
Hannah Research Foundation
1969
National Dairy Research Institute
1969
The Nuclear Spectroscopic Telescope Array (NuSTAR) mission, launched on 2012 June 13, is the first focusing high-energy X-ray telescope in orbit. NuSTAR operates band from 3 to 79 keV, extending sensitivity of far beyond ∼10 keV cutoff achieved by all previous satellites. inherently low background associated with concentrating light enables probe hard sky a more than 100-fold improvement over collimated or coded mask instruments that have operated this bandpass. Using its unprecedented...
Gravitational waves have been detected from a binary neutron star merger event, GW170817. The detection of electromagnetic radiation the same source has shown that occurred in outskirts galaxy NGC 4993, at distance 40 megaparsecs Earth. We report counterpart radio appears 16 days after allowing us to diagnose energetics and environment merger. observed emission can be explained by either collimated ultra-relativistic jet viewed off-axis, or cocoon mildly relativistic ejecta. Within 100...
Merging neutron stars offer an exquisite laboratory for simultaneously studying strong-field gravity and matter in extreme environments. We establish the physical association of electromagnetic counterpart EM170817 to gravitational waves (GW170817) detected from merging stars. By synthesizing a panchromatic dataset, we demonstrate that are long-sought production site forging heavy elements by r-process nucleosynthesis. The weak gamma-rays seen dissimilar classical short gamma-ray bursts with...
We present the calibration of Nuclear Spectroscopic Telescope Array (NuSTAR) X-ray satellite. used Crab as primary effective area calibrator and constructed a piece-wise linear spline function to modify vignetting response. The achieved residuals for all off-axis angles energies, compared assumed spectrum, are typically better than ±2% up 40 keV 5%–10% above due limited counting statistics. An empirical adjustment theoretical two-dimensional point-spread (PSF) was found using several strong...
Wide-field optical surveys have begun to uncover large samples of fast (trise ≲ 5 d), luminous (Mpeak < −18), blue transients. While commonly attributed the breakout a supernova shock into dense wind, great distances transients this class found so far hampered detailed investigation their properties. We present photometry and spectroscopy from comprehensive worldwide campaign observe AT 2018cow (ATLAS 18qqn), first fast-luminous transient be in real time at low redshift. Our spectra (<2 days...
From the first two seasons of Palomar Transient Factory, we identify three peculiar transients (PTF 09dav, PTF 10iuv, and 11bij) with five distinguishing characteristics: peak luminosity in gap between novae supernovae (MR ≈ −15.5 to −16.5 mag), rapid photometric evolution (trise 12–15 days), large photospheric velocities (≈6000–11,000 km s−1), early spectroscopic into nebular phase (≈1–3 months), spectra dominated by calcium. We also culled extensive decade-long Lick Observatory Supernova...
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...
Millisecond pulsars are thought to be neutron stars that have been spun-up by accretion of matter from a binary companion. Although most in systems, some 30% solitary, and their origin is therefore mysterious. PSR J1719-1438, 5.7 ms pulsar, was detected recent survey with the Parkes 64m radio telescope. We show it system an orbital period 2.2 h. Its companion's mass near Jupiter, but its minimum density 23 g cm$^{-3}$ suggests may ultra-low carbon white dwarf. This thus once Ultra Compact...
Abstract We present detailed submillimeter- through centimeter-wave observations of the extraordinary extragalactic transient AT2018cow. The apparent characteristics—the high radio luminosity, rise and long-lived emission plateau at millimeter bands, sub-relativistic velocity—have no precedent. A basic interpretation data suggests coupled to a fast but ( ) shock in dense medium. find that X-ray is not naturally explained by an extension radio-submm synchrotron spectrum, nor inverse Compton...
The many unusual properties of the enigmatic AT2018cow suggested that at least some subset empirical class fast blue optical transients (FBOTs) represents a genuinely new astrophysical phenomenon. Unfortunately, intrinsic rarity and fleeting nature these events have made it difficult to identify additional examples early enough acquire observations necessary constrain theoretical models. We present here Zwicky Transient Facility discovery AT2020xnd (ZTF20acigmel, "Camel") z=0.243, first...
Abstract We present early-phase panchromatic photometric and spectroscopic coverage spanning the far-ultraviolet to near-infrared regime of nearest hydrogen-rich core-collapse supernova (SN) in last 25 yr, SN 2023ixf. observe early “flash” features optical spectra due confined dense circumstellar material (CSM). high-ionization absorption lines (Fe ii , Mg ) ultraviolet from very on. also a multipeaked emission profile H α spectrum beginning at ∼16 days, which indicates ongoing interaction...
The <i>Nuclear Spectroscopic Telescope Array (NuSTAR)</i> is a NASA Small Explorer mission that will carry the first focusing hard X-ray (6 - 80 keV) telescope to orbit. <i>NuSTAR</i> offer factor 50 100 sensitivity improvement compared previous collimated or coded mask imagers have operated in this energy band. In addition, provides sub-arcminute imaging with good spectral resolution over 12-arcminute eld of view. After launch, out two-year primary science focuses on four key programs:...
Most millisecond pulsars with low-mass companions are in systems either helium-core white dwarfs or non-degenerate ("black widow" "redback") stars. A candidate counterpart to PSR J1816+4510 was identified by Kaplan et al. whose properties were suggestive of both types although identical neither. We have assembled optical spectroscopy the companion and confirm that it is part binary system a radial velocity amplitude 343 ± 7 km s−1, implying high pulsar mass, Mpsrsin 3i = 1.84 0.11 M☉, mass...
We present the X-ray timing and spectral evolution of Galactic Center magnetar SGR J1745-2900 for first ~4 months post-discovery using data obtained with Nuclear Spectroscopic Telescope Array (NuSTAR)} Swift observatories. Our analysis reveals a large increase in spin-down rate by factor 2.60 +/- 0.07 over our span. further show that change spin was likely coincident bright burst observed 2013 June Swift, if so, there no accompanying discontinuity frequency. find source 3-10 keV flux has...
Cadmium Zinc Telluride Imager (CZTI) aboard AstroSat has been regularly detecting Gamma-Ray Bursts (GRBs) since its launch in 2015. Its sensitivity to polarization measurements at energies above 100 keV allows CZTI attempt spectro-polarimetric studies of GRBs. Here, we present the first catalog GRB made by during five years operation. This presents time integrated prompt emission 20 GRBs energy range 100-600 keV. The sample includes bright which were detected within an angle 0-60 degree and...
Abstract We report observations of the optical counterpart long gamma-ray burst GRB 221009A. Due to extreme rarity being both nearby ( z = 0.151) and highly energetic E γ ,iso ≥ 10 54 erg), 221009A offers a unique opportunity probe connection between massive star core collapse relativistic jet formation across very broad range -ray properties. Adopting phenomenological power-law model for afterglow host galaxy estimates from high-resolution Hubble Space Telescope imaging, we use Bayesian...
Abstract We present a detailed investigation of photometric, spectroscopic, and polarimetric observations the Type II SN 2023ixf. Earlier studies have provided compelling evidence for delayed shock breakout from confined dense circumstellar matter (CSM) enveloping progenitor star. The temporal evolution polarization in 2023ixf phase revealed three distinct peaks at 1.4 days, 6.4 79.2 indicating an asymmetric CSM, aspherical front clumpiness low-density extended inner ejecta/He-core....
Abstract We report observations of the optical counterpart long gamma-ray burst (GRB) GRB 230812B and its associated supernova (SN) SN 2023pel. The proximity ( z = 0.36) high energy E γ ,iso ∼ 10 53 erg) make it an important event to study as a probe connection between massive star core collapse relativistic jet formation. With phenomenological power-law model for afterglow, we find late-time flattening consistent with presence SN. 2023pel has absolute peak r -band magnitude M −19.46 ± 0.18...
We report positions, velocities and metallicities of 50 ab-type RR Lyrae (RRab) stars observed in the vicinity Orphan stellar stream. Using about 30 RRab classified as being likely members stream, we study metallicity spatial extent find that stream have a wide range metallicities, from -1.5 dex to -2.7 dex. The average is -2.1 dex, identical value obtained by Newberg et al. (2010) using blue horizontal branch stars. most distant parts (40-50 kpc Sun) are 0.3 more metal-poor than closer...
X-ray polarimetry is largely an unexplored area of otherwise mature field astronomy. Except for a few early attempts during the 1970s, no dedicated polarimeter has been flown past four decades. On other hand, scientific value polarization measurement well known long time, and there significant technical progress in developing sensitive polarimeters recent years. But are approved polarimetric experiments to be near future, so it important explore capabilities existing or planned instruments...