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The synchrotron external shock model predicts the evolution of the spectral ($\beta$) and temporal ($\alpha$) indices during the gamma-ray burst (GRB) afterglow for different environmental density profiles, electron spectral indices,…

High Energy Astrophysical Phenomena · Physics 2019-10-15 Donggeun Tak , Nicola Omodei , Z. Lucas Uhm , Judith Racusin , Katsuaki Asano , Julie McEnery

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 possibility that gamma-ray bursts (GRBs) were not isotropic emissions was devised theoretically as a way to ameliorate the huge energetic budget implied by the standard fireball model for these powerful phenomena. However, the mechanism…

Astrophysics · Physics 2007-05-23 M. A. Aloy , M. Obergaulinger

A unified explanation of the variety of long-duration gamma-ray burst (GRB) light curves (LCs) is essential for identifying the dissipation mechanism and possibly the nature of their central engines. In the past, a model was proposed to…

High Energy Astrophysical Phenomena · Physics 2025-10-17 Manuele Maistrello , Lisa Ferro , Lorenzo Bazzanini , Romain Maccary , Cristiano Guidorzi

A generic synchrotron external shock model is the widely preferred paradigm used to interpret the broad-band afterglow data of gamma-ray bursts (GRBs), including predicted observable signatures from a reverse shock which have been confirmed…

High Energy Astrophysical Phenomena · Physics 2015-09-23 He Gao , Peter Mészáros

We examine the width of the gamma-ray burst (GRB) luminosity function through the distribution of GRB peak count rates, C$_{\rm{peak}}$, as detected by BATSE (\cite{batse:93}). In the context of galactic corona spatial distribution models,…

Astrophysics · Physics 2009-10-22 Andrew Ulmer , Ralph A. M. J. Wijers

Positive lags between the arrival time of different photon energies are commonly observed in Gamma-Ray Bursts (GRBs), where soft photons lag behind harder ones. However, some GRBs exhibit the opposite behavior. In particular, Fermi LAT…

High Energy Astrophysical Phenomena · Physics 2025-05-21 C. Maraventano , G. Ghirlanda , L. Nava , T. Di Salvo , W. Leone , R. Iaria , L. Burderi , A. Tsvetkova

The prompt emission mechanism of gamma-ray bursts (GRBs) is still unclear, and the time-resolved spectral analysis of GRBs is a powerful tool for studying their underlying physical processes. We performed a detailed time-resolved spectral…

High Energy Astrophysical Phenomena · Physics 2024-01-29 Wan-Kai Wang , Wei Xie , Zhi-Fu Gao , Shuo Xiao , Ai-Jun Dong , Bin Zhang , Qi-Jun Zhi

We argue that small pitch angle synchrotron emission provides an important dissipation mechanism which has to be taken into account in the models of formation of relativistic magnetized gamma-ray burst (GRB) outflows from the newborn black…

High Energy Astrophysical Phenomena · Physics 2010-08-12 A. Neronov , V. Savchenko

Understanding the origin and diversity of emission processes responsible for Gamma-ray Bursts (GRBs) remains a pressing challenge. While prompt and contemporaneous panchromatic observations have the potential to test predictions of the…

(abridged)Prompt GRB emission is often interpreted as synchrotron radiation from high-energy electrons accelerated in internal shocks. Fast synchrotron cooling predicts that the photon index below the spectral peak is alpha=-3/2. This…

High Energy Astrophysical Phenomena · Physics 2015-05-19 F. Daigne , Z. Bosnjak , Guillaume Dubus

Detection of prompt emission by Swift-XRT provides a unique tool to study how the prompt spectrum of gamma-ray bursts (GRBs) extends down to the soft X-ray band. This energy band is particularly important for prompt emission studies, since…

High Energy Astrophysical Phenomena · Physics 2018-09-05 Gor Oganesyan , Lara Nava , Giancarlo Ghirlanda , Annalisa Celotti

Synchrotron radiation of relativistic electrons is an important radiation mechanism in many astrophysical sources. In the sources where the synchrotron cooling time scale $t_c$ is shorter than the dynamical time scale $t_{dyn}$, electrons…

High Energy Astrophysical Phenomena · Physics 2015-06-15 Z. Lucas Uhm , Bing Zhang

We compare the luminosity function and rate inferred from the GBM long bursts peak flux distribution with those inferred from the Swift and BATSE peak flux distribution. We find that the GBM, BATSE and the Swift peak fluxes can be fitted by…

High Energy Astrophysical Phenomena · Physics 2009-11-05 Dafne Guetta , Elena Pian

Previous studies have found that the width of gamma-ray burst (GRB) pulse is energy dependent and that it decreases as a power-law function with increasing photon energy. In this work we have investigated the relation between the energy…

High Energy Astrophysical Phenomena · Physics 2015-06-04 Z. Y. Peng , X. H. Zhao , Y. Yin , Y. Y. Bao , L. Ma

We present the results of a comprehensive study of the luminosity function, energetics, prompt gamma-ray correlations, and classification methodology of short-hard and long-soft GRBs (SGRBs and LGRBs), based on observational data in the…

High Energy Astrophysical Phenomena · Physics 2015-08-06 Amir Shahmoradi , Robert J. Nemiroff

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

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 recently discovered GRB afterglow is believed to be described reasonably well by synchrotron emission from a slowing down relativistic shell that collides with an external medium. To compare theoretical models with afterglow…

Astrophysics · Physics 2009-10-30 Re'em Sari , Tsvi Piran , Ramesh Narayan

Statistical studies of gamma-ray burst (GRB) spectra may result in important information on the physics of GRBs. The Fermi GBM catalog contains GRB parameters (peak energy, spectral indices, intensity) estimated fitting the gamma-ray SED of…

High Energy Astrophysical Phenomena · Physics 2017-12-29 Istvan I. Racz , Lajos G. Balázs , Istvan Horvath , L. Viktor Toth , Zsolt Bagoly
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