A5029398058- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Solar and Space Plasma Dynamics
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Nuclear Physics and Applications
- Planetary Science and Exploration
- Particle Detector Development and Performance
- Calibration and Measurement Techniques
- Advanced Semiconductor Detectors and Materials
- Advanced X-ray Imaging Techniques
- Ionosphere and magnetosphere dynamics
- Astronomical Observations and Instrumentation
- Advanced X-ray and CT Imaging
- Radiation Therapy and Dosimetry
- Space Exploration and Technology
- High-pressure geophysics and materials
- Geophysics and Gravity Measurements
- Radiation Detection and Scintillator Technologies
- Solar Radiation and Photovoltaics
- Neutrino Physics Research
- Astronomy and Astrophysical Research
- Mechanics and Biomechanics Studies
Physical Research Laboratory
2015-2024
National Institute for Astrophysics
2023
Indian Institute of Technology Gandhinagar
2021-2022
GRB 160821A is the third most energetic gamma ray burst observed by {\it Fermi} gamma-ray space telescope. Based on observations made Cadmium Zinc Telluride Imager (CZTI) board AstroSat}, here we report conclusive evidence to date of (i) high linear polarization ($66^{+26}_{-27} \%$; $5.3 \sigma$ detection), and (ii) variation its angle with time happening twice during rise decay phase at $3.5 $3.1 detections respectively. All confidence levels are reported for two parameters interest. These...
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 present a comprehensive multiwavelength spectral analysis of the black hole (BH) X-ray binary MAXI J1820+070 during its 2018 outburst, utilizing AstroSat far-UV, soft X-ray, and hard data, along with (quasi-)simultaneous optical data from Las Cumbres Observatory NICER, respectively. In state, we detect UV/optical excess components over above intrinsic accretion disk emission ( kT in ∼ 0.58 keV) steep power-law component. The is consistent high-temperature blackbody 0.79 keV),...
The Solar X-ray Spectrometer (XSM) payload onboard Chandrayaan-2 provides disk-integrated solar spectra in the 1-15 keV energy range with an resolution of 180 eV (at 5.9 keV) and a cadence 1~second. During period from September 2019 to May 2020, covering minimum Cycle 24, it observed nine B-class flares ranging B1.3 B4.5. Using time-resolved spectroscopic analysis during these flares, we examined evolution temperature, emission measure, absolute elemental abundances four elements -- Mg, Al,...
ABSTRACT AstroSat is a multi-wavelength satellite launched on 2015 September 28. The CZT Imager of its very first day operation detected long duration gamma-ray burst (GRB), namely GRB 151006A. Using the off-axis imaging and spectral response instrument, we demonstrate that can localize this correctly to about few degrees, it provide, in conjunction with Swift , parameters similar those obtained from Fermi /GBM. Hence, would be useful addition currently operating instruments ( )....
Abstract X-ray and gamma-ray polarization measurements of the prompt emission bursts (GRBs) are believed to be extremely important for testing various models GRBs. So far, available hard GRB have not significantly constrained models, particularly because difficulty measuring in these bands. The CZT Imager (CZTI) on board AstroSat is primarily an spectroscopic instrument that also works as a wide-angle monitor due transparency its support structure above 100 keV. It has experimentally...
Solar X-ray Monitor (XSM) is one of the scientific instruments onboard Chandrayaan-2 orbiter.The XSM along with instrument CLASS (Chandra's Large Area soft Spectrometer) comprise remote fluorescence spectroscopy experiment mission an objective to determine elemental composition lunar surface on a global scale.XSM will measure solar X-rays in energy range 1-15 keV using state-of-the-art silicon drift detector.The flight model payload has been designed, realized and characterized for various...
Solar flares, with energies ranging over several orders of magnitude, result from impulsive release energy due to magnetic reconnection in the corona. Barring a handful, almost all microflares observed X-rays are associated solar active regions. Here we present, for first time, comprehensive analysis large sample quiet Sun soft by X-ray Monitor (XSM) on board Chandrayaan-2 mission during 2019-20 minimum. A total 98 having peak flux below GOES A-level were XSM observations spanning 76 days....
Elements with low First Ionization Potential (FIP) are known to be three four times more abundant in active region loops of the solar corona than photosphere. There have been observations suggesting that this observed "FIP bias" may different other parts and such thus important understanding underlying mechanism. The Solar X-ray Monitor (XSM) on board Chandrayaan-2 mission carried out spectroscopic Sun soft X-rays during 2019-20 minimum, considered quietest minimum past century. These...
Small-scale impulsive events, known as nanoflares, are thought to be one of the prime candidates that can keep solar corona hot at its multi-million Kelvin temperature. Individual nanoflares difficult detect with current generation instruments; however, their presence inferred through indirect techniques such a Differential Emission Measure (DEM) analysis. Here we employ this technique investigate possibility nanoflare heating quiet during minimum cycle 24. During minimum, active regions...
We present multi-wavelength follow-up campaigns by the AstroSat-CZTI and GROWTH collaborations to search for an electromagnetic counterpart gravitational wave event GW170104. At time of GW170104 trigger, AstroSat CZTI field-of-view covered 50.3\% sky localization. do not detect any hard X-ray (>100 keV) signal at this time, place upper limit $\approx 4.5 \times 10^{-7}~{\rm erg~cm}^{-2}{\rm~s}^{-1}$ a 1\,s timescale. Separately, ATLAS survey reported rapidly fading optical source dubbed...
Abstract Cygnus X-1, the well-known accreting black hole system, exhibits several observational features hinting at an intricate interplay between accretion disk, its atmosphere known as corona, and putative relativistic jet. It has been extensively studied using all available methods, including newly technique of sensitive X-ray polarimetry. polarization characteristics are distinct for coronal jet emissions. The low measured below ∼100 keV is understood arising from corona. In contrast,...
Abstract We perform broadband (0.7–100 keV) spectral analysis of five hard state observations the low-mass black hole X-ray binary GX 339–4 taken by AstroSat during rising phase three outbursts from 2019 to 2022. find that outburst in 2021 was only successful/full outburst, while source unable make transition soft other two and Our employs different model combinations, requiring separate Comptonizing regions their associated reflection components excess emission. The harder component...
We present X-ray light curves of Cygnus X-3 as measured by the recently launched AstroSat satellite. The curve folded over binary period 4.8 hours shows a remarkable stability past 45 years and we find that can use this information to measure zero point better than 100 s. revisit historical phase measurements examine years. new ephemeris with derivative determined an accuracy much previously reported. do not any evidence for second in variation. precise measurements, however, indicate hint...