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Although Gamma Ray Bursts (GRBs) have been detected for many decades, the lack of knowledge regarding the radiation mechanism that produces the energetic flash of radiation, or prompt emission, from these events has prevented the full use…

High Energy Astrophysical Phenomena · Physics 2022-02-23 Tyler Parsotan , Davide Lazzati

In this catalog we present the updated set of spectral analyses of GRBs detected by the Fermi Gamma-Ray Burst Monitor (GBM) during its first four years of operation. It contains two types of spectra, time-integrated spectral fits and…

We compare the properties of optically dark GRBs, defined by the optical-to-X-ray spectral index beta_OX<0.5, and normal ones discovered by the Swift satellite before the year 2008 in a statistical way, using data collected from the…

High Energy Astrophysical Phenomena · Physics 2009-09-24 W. Zheng , J. Deng , J. Wang

Cosmological models that include suppression of the power spectrum of density fluctuations on small scales exhibit an exponential reduction of high-redshift, non-linear structures, including a reduction in the rate of gamma ray bursts…

Astrophysics · Physics 2009-11-10 Andrei Mesinger , Rosalba Perna , Zoltan Haiman

The origin of prompt emission in $\gamma$-ray bursts (GRBs) is highly debated topic. The observed spectra are supposed to play a crucial role in constraining the location of the emitting region, the strength of the magnetic field and the…

High Energy Astrophysical Phenomena · Physics 2020-06-26 Gor Oganesyan

Gamma-Ray Bursts (GRBs) are fascinating events due to their panchromatic nature. Their afterglow emission is observed from sub-TeV energies to radio wavelengths. We investigate GRBs that present an optical plateau, leveraging on the…

High Energy Astrophysical Phenomena · Physics 2021-01-06 M. G. Dainotti , S. Livermore , D. A. Kann , L. Li , S. Oates , S. Yi , B. Zhang , B. Gendre , B. Cenko , N. Fraija

The paradigm for GRB prompt emission is changing. Since early in the CGRO era, the empirical Band function has been considered a good description of the keV-MeV spectra although its shape is very often inconsistent with the predictions of…

High Energy Astrophysical Phenomena · Physics 2016-03-16 S. Guiriec , M. M. Gonzalez , J. R. Sacahui , C. Kouveliotou , N. Gehrels , J. McEnery

Optical broad-band spectral shape measurements of gamma-ray bursts (GRBs) are typically made starting an hour or more after the trigger event. With our automated, rapid-response system, the Burst Simultaneous Three-channel Imager (BSTI) on…

The Robotic Optical Transient Search Experiment (ROTSE) seeks to measure simultaneous and early afterglow optical emission from gamma-ray bursts (GRBs). A search for optical counterparts to six GRBs with localization errors of 1 square…

The long-lasting tension between the observed spectra of gamma ray bursts (GRBs) and the predicted synchrotron emission spectrum might be solved if electrons do not completely cool. Evidence for incomplete cooling was recently found in…

High Energy Astrophysical Phenomena · Physics 2019-05-15 M. E. Ravasio , G. Ghirlanda , L. Nava , G. Ghisellini

We collected the optical light curve data of 227 gamma-ray bursts (GRBs) observed with the TAROT, COATLI, and RATIR telescopes. These consist of 133 detections and 94 upper limits. We constructed average light curves in the observer and…

We study 7 Gamma Ray Bursts (GRBs), detected both by the BATSE instrument, on-board the Compton Gamma Ray Observatory, and by the Wide Field Camera (WFC), on-board BeppoSAX. These bursts have measured spectroscopic redshifts and are a…

Astrophysics · Physics 2009-06-23 G. Ghirlanda , Z. Bosnjak , G. Ghisellini , F. Tavecchio , C. Firmani

The emission process responsible for the so-called "prompt" emission of gamma-ray bursts is still unknown. A number of empirical models fitting the typical spectrum still lack a satisfactory interpretation. A few GRB spectral catalogues…

High Energy Astrophysical Phenomena · Physics 2011-05-03 C. Guidorzi , M. Lacapra , F. Frontera , E. Montanari , L. Amati , F. Calura , L. Nicastro , M. Orlandini

We present the second Swift Burst Alert Telescope (BAT) catalog of gamma-ray bursts (GRBs), which contains 476 bursts detected by the BAT between 2004 December 19 and 2009 December 21. This catalog (hereafter the BAT2 catalog) presents…

The prompt phase X- and $\gamma$-ray light curves of gamma-ray bursts (GRBs) exhibit erratic and complex behaviour, often with multiple pulses. The temporal shape of individual pulses is often modelled as 'fast rise exponential decay'…

High Energy Astrophysical Phenomena · Physics 2025-07-14 A Gowri , A. Pe'er , F. Ryde , H. Dereli-Bégué

We examined the properties of a sample of BATSE Gamma--Ray Bursts (GRBs) comprising events which have indications of association with a supernova (SN), some on the basis of indications of re--brightening in the optical afterglow light…

Astrophysics · Physics 2016-08-30 Z. Bosnjak , A. Celotti , G. Ghirlanda , M. Della Valle , E. Pian

Four years after the launch the Swift satellite the nature of the GRBs broadband afterglow behaviour is still an open issue. The standard external shock fireball model cannot easily explain the combined temporal and spectral properties of…

High Energy Astrophysical Phenomena · Physics 2011-05-06 M. Nardini , G. Ghisellini , G. Ghirlanda , A. Celotti

The properties of the spectral evolution during the prompt emission phase of gamma-ray bursts (GRBs), which are closely related to the radiation mechanism (synchrotron or photosphere), are still a subject of debate. Two spectral evolution…

High Energy Astrophysical Phenomena · Physics 2026-04-21 Liang Li

The earliest BTA (SAO RAS 6-m telescope) spectroscopic observations of the GRB 030329 optical transient (OT) are presented, which almost coincide in time with the "first break" ($t\sim 0.5$ day after the GRB) of the OT light curve. The…

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