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The radiation mechanisms powering Gamma-ray bursts (GRBs) and their physical processes remain one of the unresolved questions in high-energy astrophysics. Spectro-polarimetric observations of exceptionally bright GRBs provide a powerful…

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

The origin of the prompt emission in gamma-ray bursts (GRBs) is still an unsolved problem and several different mechanisms have been suggested. Here we fit Fermi GRB data with a photospheric emission model which includes dissipation of the…

High Energy Astrophysical Phenomena · Physics 2015-09-30 Björn Ahlgren , Josefin Larsson , Tanja Nymark , Felix Ryde , Asaf Pe'er

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

The prompt emission of the long, smooth, and single-pulsed gamma-ray burst, GRB $\textit{141028A}$, is analyzed under the guise of an external shock model. First, we fit the $\gamma$-ray spectrum with a two-component photon model, namely…

High Energy Astrophysical Phenomena · Physics 2016-05-25 J. Michael Burgess , Damien Bégué , Felix Ryde , Nicola Omodei , Asaf Pe'er , J. L. Racusin , A. Cucchiara

The modified version of a bullet model for gamma ray bursts is studied. The central engine of the source produces multiple sub-jets that are contained within a cone. The emission of photons in the source frame of a sub-jet either takes part…

Astrophysics · Physics 2009-11-13 A. Janiuk , B. Czerny , R. Moderski , D. B. Cline , C. Matthey , S. Otwinowski

The emission processes active in the highly relativistic jets of gamma-ray bursts (GRBs) remain unknown. In this paper we propose a new measure to describe spectra: the width of the $EF_E$ spectrum, a quantity dependent only on finding a…

High Energy Astrophysical Phenomena · Physics 2015-01-20 Magnus Axelsson , Luis Borgonovo

The observational diversity of optical emission, which coincides with prompt gamma-ray bursts (GRBs), has been discovered in the recent Swift era. We show that on the assumption of the synchrotron radiation for the observed energy range…

Astrophysics · Physics 2009-11-13 Hirotsugu Doi , Kentaro Takami , Ryo Yamazaki

The detection of delayed X-ray, optical and radio emission, "afterglow", associated with $\gamma$-ray bursts (GRBs) is consistent with fireball models, where the emission are produced by relativistic expanding blast wave, driven by…

Astrophysics · Physics 2009-10-30 D. M. Wei , T. Lu

We consider the evidence for very hard low energy spectra during the prompt phase of Gamma-Ray Bursts (GRB). In particular we examine the spectral evolution of GRB 980306 together with the detailed analysis of some other bursts already…

Astrophysics · Physics 2009-11-07 Giancarlo Ghirlanda , Annalisa Celotti , Gabriele Ghisellini

Gamma ray bursts (GRB) occur at random points in the sky at cosmological distances. The spectra evolve through X-ray, optical region to possibly radio frequency. Though there are some models, the origin and time evolution of GRB are not…

Astrophysics · Physics 2007-05-23 Manoj Thulasidas

The long standing problem of identifying the emission mechanism operating in gamma-ray bursts (GRBs) has produced a myriad of possible models that have the potential of explaining the observations. Generally, the empirical Band function is…

High Energy Astrophysical Phenomena · Physics 2014-10-29 J. Michael Burgess , Felix Ryde , Hoi-Fung Yu

The origins of the main burst and second burst of gamma-ray bursts (GRBs) and the composition of their jets remain uncertain. To explore this complex subject more thoroughly, we conduct a spectral analysis on 18 GRBs with a main and a…

High Energy Astrophysical Phenomena · Physics 2025-05-12 Ze-Lian Du , Zhao-Yang Peng , Jia-Ming Chen , Yue Yin , Ting Li

The central engine in long gamma-ray bursts (GRBs) is thought to be a compact object produced by the core collapse of massive stars, but its exact nature (black hole or millisecond magnetar) is still debatable. Although the central engine…

High Energy Astrophysical Phenomena · Physics 2020-06-24 M. Petropoulou , P. Beniamini , G. Vasilopoulos , D. Giannios , R. Barniol Duran

Several trends have been identified in the prompt gamma-ray burst (GRB) emission: e.g. hard-to-soft evolution, pulse width evolution with energy, time lags, hardness-intensity/-fluence correlations. Recently Fermi has significantly extended…

High Energy Astrophysical Phenomena · Physics 2015-06-19 Z. Bosnjak , F. Daigne

Extended, fading emissions in multi-wavelength are observed following Gamma-ray bursts (GRBs). Recent broad-band observational campaigns led by the Swift Observatory reveal rich features of these GRB afterglows. Here we review the latest…

Astrophysics · Physics 2009-11-11 Bing Zhang

In the external shock model, gamma-ray burst (GRB) emissions are produced by the energization and deceleration of a thin relativistic blast wave due to its interactions with the circumburst medium (CBM). We study the physical properties of…

Astrophysics · Physics 2009-10-31 Charles D. Dermer , Markus Boettcher , J. Chiang

The successful launch and operation of NASA's Swift Gamma-Ray Burst Explorer open a new era for the multi-wavelength study of the very early afterglow phase of gamma-ray bursts (GRBs). GRB early afterglow information is essential to explore…

Astrophysics · Physics 2009-11-13 Bing Zhang

After seven years of science operation, the Fermi mission has brought great advances in the study of Gamma-ray Bursts (GRBs). Over 1600 GRBs have been detected by the Gamma-ray Burst Monitor, and more than 100 of these are also detected by…

High Energy Astrophysical Phenomena · Physics 2015-07-19 Elisabetta Bissaldi , Francesco Longo , Nicola Omodei , Giacomo Vianello , Andreas von Kienlin

Gamma-ray bursts (GRB) are generally believed to be efficient particle accelerators. In the presence of energetic protons in a GRB jet, interactions between these protons and intense radiation field of the GRB are supposed to induce…

High Energy Astrophysical Phenomena · Physics 2023-02-01 Ruo-Yu Liu , Hai-Ming Zhang , Xiang-Yu Wang