P. N. Bhat
A5027924574- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Particle Detector Development and Performance
- Pulsars and Gravitational Waves Research
- Astrophysical Phenomena and Observations
- Nuclear Physics and Applications
- Astro and Planetary Science
- Dark Matter and Cosmic Phenomena
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Radiation Detection and Scintillator Technologies
- Earthquake Detection and Analysis
- Particle physics theoretical and experimental studies
- Particle Accelerators and Free-Electron Lasers
- Atomic and Subatomic Physics Research
- Lightning and Electromagnetic Phenomena
- Ionosphere and magnetosphere dynamics
- Geophysics and Gravity Measurements
- Stellar, planetary, and galactic studies
- Radio Astronomy Observations and Technology
- Solar and Space Plasma Dynamics
- Advanced X-ray and CT Imaging
- Adaptive optics and wavefront sensing
- CCD and CMOS Imaging Sensors
- Neutrino Physics Research
University of Alabama in Huntsville
2014-2024
Raisoni Group of Institutions
2024
Amrita Vishwa Vidyapeetham
2024
RTX (United States)
2021
National Space Science and Technology Center
2007-2015
Bhabha Atomic Research Centre
1989-2015
University of Alabama
2009-2011
Universities Space Research Association
2009-2011
Marshall Space Flight Center
1992-2011
Max Planck Institute for Extraterrestrial Physics
2008-2011
Detectors aboard the Compton Gamma Ray Observatory have observed an unexplained terrestrial phenomenon: brief, intense flashes of gamma rays. These must originate in atmosphere at altitudes above least 30 kilometers order to escape atmospheric absorption and reach orbiting detectors. At a dozen such events been detected over past 2 years. The photon spectra from are very hard (peaking high-energy portion spectrum) consistent with bremsstrahlung emission energetic (million—electron volt)...
The Gamma-Ray Burst Monitor (GBM) will significantly augment the science return from Fermi Observatory in study of gamma-ray bursts (GRBs). primary objective GBM is to extend energy range over which are observed downward Large Area Telescope (LAT) on into hard X-ray where extensive previous data sets exist. A secondary compute burst locations onboard allow re-orienting spacecraft so that LAT can observe delayed emission bright bursts. uses an array 12 sodium iodide scintillators and two...
Gamma-ray bursts (GRBs) are highly energetic explosions signaling the death of massive stars in distant galaxies. The Burst Monitor and Large Area Telescope onboard Fermi Observatory together record GRBs over a broad energy range spanning about 7 decades gammaray energy. In September 2008, observed exceptionally luminous GRB 080916C, with largest apparent release yet measured. high-energy gamma rays to start later persist longer than lower photons. A simple spectral form fits entire...
We report on the observation of bright, long gamma-ray burst, GRB 090902B, by Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) instruments on-board Fermi observatory. This was one brightest GRBs to have been observed LAT, which detected several hundred photons during prompt phase. With a redshift z = 1.822, this burst is among most luminous Fermi. Time-resolved spectral analysis reveals significant power-law component in LAT data that distinct from usual Band model emission seen...
With an instantaneous view of 70% the sky, Fermi Gamma-ray Burst Monitor (GBM) is excellent partner in search for electromagnetic counterparts to gravitational wave (GW) events. GBM observations at time Laser Interferometer Gravitational-wave Observatory (LIGO) event GW150914 reveal presence a weak transient above 50 keV, 0.4~s after GW event, with false alarm probability 0.0022 (2.9$\sigma$). This lasting 1 s was not detected by any other instrument and does appear connected previously...
We present detailed observations of the bright short-hard gamma-ray burst GRB 090510 made with Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) on board Fermi observatory. is first detected by LAT that shows strong evidence for a deviation from Band spectral fitting function during prompt emission phase. The time-integrated spectrum fit sum $\Epeak = 3.9\pm 0.3$\,MeV, which highest yet measured, hard power-law component photon index $-1.62\pm 0.03$ dominates below...
The Gamma‐ray Burst Monitor (GBM) on the Fermi Space Telescope detected 12 intense terrestrial gamma ray flashes (TGFs) during its first year of observation. Typical maximum energies for most TGFs are ∼30 MeV, with one TGF having a 38 MeV photon; two softer and longer than others. After correcting instrumental effects, representative bright is found to have fluence ∼0.7 photons cm −2 . Pulses either symmetrical or faster risetimes fall times; they well fit Gaussian lognormal functions....
In three years of observations since the beginning nominal science operations in August 2008, Large Area Telescope (LAT) on board Fermi Gamma Ray Space has observed high-energy (>20 MeV) \gamma-ray emission from 35 gamma-ray bursts (GRBs). Among these, 28 GRBs have been detected above 100 MeV and 7 ~ 20 MeV. The first Fermi-LAT catalog is a compilation these detections provides systematic study for time. To generate catalog, we examined 733 by Gamma-Ray Burst Monitor (GBM) processed each...
We present the fourth in a series of catalogs gamma-ray bursts (GRBs) observed with Fermi's Gamma-Ray Burst Monitor (Fermi-GBM). It extends six year catalog by four more years, now covering ten time period from trigger enabling on 2008 July 12 to 2018 11. During this GBM triggered almost twice day transient events which we identifyied 2356 as cosmic GRBs. Additional were due solar are events, magnetar burst activities, and terrestrial flashes. The intention GRB is provide updated information...
Observations of GRB 100724B with the Fermi Gamma-Ray Burst Monitor find that spectrum is dominated by typical Band functional form, which usually taken to represent a non-thermal emission component, but also includes statistically highly significant thermal spectral contribution. The simultaneous observation and components allows us confidently identify two components. fact these seem vary independently favors idea component photospheric origin while dominant occurs at larger radii. Our...
Since its launch in 2008, the Fermi Gamma-ray Burst Monitor (GBM) has triggered and located on average approximately two gamma-ray bursts (GRB) every three days. Here we present third of a series catalogs GRBs detected by GBM, extending second catalog more years, through middle July 2014. The resulting list includes 1405 triggers identified as GRBs. intention GBM GRB is to provide information community most important observables For each location main characteristics prompt emission,...
In this catalog we present the updated set of spectral analyses GRBs detected by Fermi Gamma-Ray Burst Monitor (GBM) during its first four years operation. It contains two types spectra, time-integrated fits and at brightest time bin, from 943 triggered GRBs. Four different models were fitted to data, resulting in a compendium more than 7500 spectra. The analysis was performed similarly, but not identically Goldstein et al. 2012. All 487 have been re-fitted using same methodology as that 456...
Abstract The Large Area Telescope (LAT) aboard the Fermi spacecraft routinely observes high-energy emission from gamma-ray bursts (GRBs). Here we present second catalog of LAT-detected GRBs, covering first 10 yr operations, 2008 to 2018 August 4. A total 186 GRBs are found; these, 91 show in range 30–100 MeV (17 which seen only this band) and 169 detected above 100 MeV. Most these sources were discovered by other instruments ( /GBM, Swift /BAT, AGILE, INTEGRAL ) or reported Interplanetary...
This is the second of a series catalogs gamma-ray bursts (GRBs) observed with Fermi Gamma-ray Burst Monitor (GBM). It extends first two-year catalog by two more years, resulting in an overall list 953 GBM triggered GRBs. The intention GRB to provide information community on most important observables detected For each location and main characteristics prompt emission, duration, peak flux fluence are derived. latter quantities calculated for 50 - 300 keV energy band, where maximum release...
Abstract We report the discovery of GRB 221009A, highest flux gamma-ray burst (GRB) ever observed by Fermi Gamma-ray Burst Monitor (Fermi-GBM). This has continuous prompt emission lasting more than 600 s, which smoothly transitions to afterglow visible in Fermi-GBM energy range (8 keV–40 MeV), and total energetics higher any other sample. By using a variety new existing analysis techniques we probe spectral temporal evolution 221009A. find no prior trigger time ( t 0 ; 2022 October 9 at...
We report on the observation of bright, long gamma-ray burst, GRB 090926A, by Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) instruments board \Fermi\ Space Telescope. 090926A shares several features with other bright LAT bursts. In particular, it clearly shows a short spike in light curve that is present all detectors see this turn suggests there common region emission across entire energy range. addition, while separate high-energy power-law component has already been...
We present systematic spectral analyses of GRBs detected by the Fermi Gamma-Ray Burst Monitor (GBM) during its first two years operation. This catalog contains types spectra extracted from 487 GRBs, and fitting four different models, this results in a compendium over 3800 spectra. The models were selected based on their empirical importance to shape many analysis performed was devised be as thorough objective possible. describe detail our procedure criteria for analyses, bulk form parameter...
GRB110721A was observed by the Fermi Gamma-ray Space Telescope using its two instruments Large Area (LAT) and Burst Monitor (GBM). The burst consisted of one major emission episode which lasted for ~24.5 seconds (in GBM) had a peak flux 5.7\pm0.2 x 10^{-5} erg/s/cm^2. time-resolved spectrum is best modeled with combination Band function blackbody spectrum. energy component initially 15\pm2 MeV, highest value ever detected in GRB. This measurement made possible combining GBM/BGO data LAT Low...
[1] Terrestrial Gamma-ray Flashes (TGFs) are brief pulses of energetic radiation observed in low-earth orbit. They associated with thunderstorms and lightning have been both as gamma-ray electron flashes depending on the position spacecraft respect to source. While TGFs detected short lasting less than 1 ms, most seen by Fermi Burst Monitor (GBM) durations greater ms are, instead, result electrons traveling from sources along geomagnetic field lines. We perform spectral analysis three...
The short GRB 120323A had the highest flux ever detected with Gamma-Ray Burst Monitor on board Fermi Space Telescope. Here we study its remarkable spectral properties and their evolution using two models: (1) a single emission component scenario, where spectrum is modeled by empirical Band function (a broken power law), (2) two-component thermal Planck-like function) observed simultaneously non-thermal function). We find that latter model fits integrated burst significantly better than...
The Crab Nebula is the only hard X-ray source in sky that both bright enough and steady to be easily used as a standard candle. As result, it has been normalization by most X-ray/gamma-ray telescopes. Although small-scale variations nebula are well known, since start of science operations Fermi Gamma-ray Burst Monitor (GBM) 2008 August, ∼7% (70 mCrab) decline observed overall flux 15–50 keV band, measured with Earth occultation technique. This independently confirmed ∼15–50 band three other...
A new data mode and analysis methods are used to detect Terrestrial Gamma‐ray Flashes (TGFs) with the Fermi Burst Monitor (GBM) 10 times more frequently than previously. In 1037 h of observations at over regions for which TGFs expected, 384 were found in addition 39 two Electron Beam events already detected without methodology. Cosmic ray showers be an important background; they show characteristic signatures both GBM Large Area Telescope Calorimeter that enable their removal, leaving a...
The Fermi Gamma-ray Burst Monitor (GBM) is designed to enhance the scientific return from in studying gamma-ray bursts (GRBs). In its first two years of operation GBM triggered on 491 GRBs. We summarize criteria used for triggering and quantify general characteristics GRBs, including their locations, durations, peak flux, fluence. This catalog an official product science team, data files containing complete results are available High-Energy Astrophysics Science Archive Research Center.