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Gamma-ray bursts (GRBs) are the universe's most energetic phenomena (isotropic luminosity $\sim 10^{51} - 10^{54}$ ergs/s) lasting for a very short duration ($\sim$ milliseconds - a few seconds). Even after an average of one GRB detected…

High Energy Astrophysical Phenomena · Physics 2026-05-13 Soumya Gupta , Sunder Sahayanathan , Saharsh Shanu , Rishabh Nath

Aims. The aim of the study is to constrain the physics of gamma-ray bursts (GRBs) by analysing the multi-wavelength afterglow data set of GRB 121024A that covers the full range from radio to X-rays. Methods. Using multi-epoch broad-band…

The origin of prompt emission in GRBs is not yet well understood. The simplest and most popular model is Synchrotron, Self-Compton (SSC) emission produced by internal shocks inside an ultra-relativistic jet. However, recent observations of…

Cosmology and Nongalactic Astrophysics · Physics 2015-03-17 Houri Ziaeepour , Brian Gardner

We performed time-resolved spectroscopy on a sample of 38 single pulses from 37 gamma-ray bursts detected by the Fermi/Gamma-ray Burst Monitor during its first 9 years of mission. For the first time a fully Bayesian approach is applied. A…

High Energy Astrophysical Phenomena · Physics 2020-01-08 Hoi-Fung Yu , Hüsne Dereli-Bégué , Felix Ryde

Gamma-ray bursts (GRBs) are highly variable and exhibit strong spectral evolution. In particular, the emission properties vary from pulse to pulse in multipulse bursts. Here we present a time-resolved Bayesian spectral analysis of a…

High Energy Astrophysical Phenomena · Physics 2021-12-20 Liang Li , Felix Ryde , Asaf Pe'er , Hoi-Fung Yu , Zeynep Acuner

The emission mechanism of the gamma-ray bursts (GRBs) is still a matter of debates. The standard synchrotron energy spectrum of cooling electrons F_E ~ E^{-1/2} is much too soft to account for the majority of the observed spectral slopes.…

Astrophysics · Physics 2009-11-10 Boris E. Stern , Juri Poutanen

We present the time integrated and time resolved spectral analysis of a sample of bright bursts selected with F_{peak}>20 phot cm^{-2} sec^{-1} from the BATSE archive. We fitted four different spectral models to the pulse time integrated…

Astrophysics · Physics 2009-11-07 G. Ghirlanda , A. Celotti , G. Ghisellini

The spectral shape of the prompt emissions of gamma-ray bursts (GRBs) is typically expressed by the Band function: smooth joining of two power-law functions for high-energy and low-energy regions. To reveal the origin of the Band function,…

High Energy Astrophysical Phenomena · Physics 2015-10-21 Katsuaki Asano , Toshio Terasawa

This paper presents a study on the spectral evolution of gamma-ray burst (GRB) prompt emissions observed with the Suzaku Wide-band All-sky Monitor (WAM). By making use of the WAM data archive, 6 bright GRBs exhibiting 7 well-separated…

High Energy Astrophysical Phenomena · Physics 2015-05-30 Makoto S. Tashiro , Kaori Onda , Kazutaka Yamaoka , Masahiro Ohno , Satoshi Sugita , Takeshi Uehara , Hiromi Seta

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

A leading mechanism for producing cosmological gamma-ray bursts (GRBs) is via ultra-relativistic particles in an expanding fireball. The kinetic energy of the particles is converted into thermal energy in a forward shock and a reverse…

Astrophysics · Physics 2009-10-28 Re'em Sari , Ramesh Narayan , Tsvi Piran

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

We demonstrate that distinguishable gamma-ray burst pulses exhibit similar behaviors as evidenced by correlations among the observable pulse properties of duration, peak luminosity, fluence, spectral hardness, energy-dependent lag, and…

High Energy Astrophysical Phenomena · Physics 2015-05-27 Jon Hakkila , Robert D. Preece

We investigate the dynamics and radiation from a relativistic blast-wave which decelerates as it sweeps up ambient matter. The bulk kinetic energy of the blast-wave shell is converted into internal energy by the process of accreting…

Astrophysics · Physics 2016-08-30 J. Chiang , C. D. Dermer

The prompt emission phase of gamma-ray bursts (GRBs) exhibits two distinct patterns of the peak-energy ($E_p$) evolution, i.e., time-resolved spectral analyses of $\nu F_{\nu}$ spectra of broad pulses reveal (1) "hard-to-soft" and (2)…

High Energy Astrophysical Phenomena · Physics 2018-12-26 Z. Lucas Uhm , Bing Zhang , Judith Racusin

We present the time integrated and time resolved spectral analysis of a sample of bright bursts selected from the BATSE archive. We fitted four different spectral models to the time integrated and time resolved spectra of the flux pulses.…

Astrophysics · Physics 2009-11-07 G. Ghirlanda , A. Celotti , G. Ghisellini

In order to better understand the physical origin of short duration gamma-ray bursts (GRBs), we perform time-resolved spectral analysis on a sample of 70 pulses in 68 short GRBs with burst duration $T_{90}\lesssim2$ s detected by the…

High Energy Astrophysical Phenomena · Physics 2020-07-22 Hüsne Dereli-Bégué , Asaf Pe'er , Felix Ryde

The typical spectrum of the prompt emission of gamma-ray bursts (GRBs) indicates that the electron cooling is suppressed in spite of the strong magnetic field in the standard synchrotron model. Recent Particle-in-Cell simulations show that…

High Energy Astrophysical Phenomena · Physics 2022-07-07 Ryota Goto , Katsuaki Asano

Synchrotron emission is believed to be a major radiation mechanism during gamma-ray bursts' (GRBs) prompt emission phase. A significant drawback of this assumption is that the theoretical predicted spectrum, calculated within the framework…

Astrophysics · Physics 2008-11-26 Asaf Pe'er , Bing Zhang

There is no consensus on the emission mechanism of $\gamma$-ray bursts (GRBs). A synchrotron model can produce $\gamma$-ray spectra with the empirical Band function form, from a piece-wise two-power-law electron energy distribution (2EPLS).…

High Energy Astrophysical Phenomena · Physics 2019-09-06 Bruce Grossan , Pawan Kumar , George F. Smoot