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Gamma-ray bursts (GRBs) are the most powerful electromagnetic outbursts in the Universe and emit a vast amount of their energy in the form of gamma rays. Their duration is extremely short on cosmic timescales, but they show a wealth of time…

High Energy Astrophysical Phenomena · Physics 2025-12-11 Else Magnus , Jannes Loonen , Rose S. Stanley , Paul Coppin , Krijn D. de Vries , Nick van Eijndhoven

The Space-based multiband astronomical Variable Objects Monitor (SVOM), detected its first short gamma-ray burst, GRB 240715A, in-flight, which was jointly observed by Fermi. Based on observational data of SVOM/GRM and Fermi/GBM, we perform…

We introduce a simple model to explain the time-reversed and stretched residuals in gamma-ray burst (GRB) pulse light curves. In this model an impactor wave in an expanding GRB jet accelerates from subluminal to superluminal velocities, or…

High Energy Astrophysical Phenomena · Physics 2019-10-02 Jon Hakkila , Robert Nemiroff

The analysis of gamma-ray burst (GRB) spectra often relies on empirical models lacking a distinct physical explanation. Previous attempts to couple physical models with observed data focus on individual burst studies, fitting models to…

High Energy Astrophysical Phenomena · Physics 2024-02-20 Zhen-Yu Yan , Jun Yang , Xiao-Hong Zhao , Yan-Zhi Meng , Bin-Bin Zhang

We present X-ray light curves (1.5-12 keV) for fifteen gamma-ray bursts (GRBs) detected by the All-Sky Monitor on the Rossi X-ray Timing Explorer. We compare these soft X-ray light curves with count rate histories obtained by the…

Time-resolved spectroscopy is performed on eight bright, long gamma-ray bursts (GRBs) dominated by single emission pulses that were observed with the {\it Fermi Gamma-ray Space Telescope}. Fitting the prompt radiation of GRBs by empirical…

In this paper, we explore time resolved Gamma-Ray Burst (GRB) spectra in the context of the synchrotron emission model presented in Lloyd and Petrosian (2000; LP00). First, we show that our model - which involves three distinct emission…

Astrophysics · Physics 2009-11-07 Nicole M. Lloyd-Ronning , Vahe' Petrosian

We make a detailed pulse-wise study of gamma-ray bursts (GRBs) with known redshift detected by \emph{Fermi}/Gamma Ray Burst Monitor (GBM). The sample contains 19 GRBs with 43 pulses. We find that the average peak energy is correlated to the…

High Energy Astrophysical Phenomena · Physics 2015-06-17 Rupal Basak , A. R. Rao

GRB 090618 was simultaneously detected by Swift-BAT and Fermi-GBM. Its light curve shows two emission episodes consisting of four prominent pulses. The pulse in the first episode (episode A) has a smoother morphology than the three pulses…

High Energy Astrophysical Phenomena · Physics 2012-04-09 Fu-Wen Zhang

We present a simple, semi-analytical model to explain GRB temporal and spectral properties in the context of the internal shock model. Each individual pulse in the temporal profiles is produced by the deceleration of fast moving material by…

Astrophysics · Physics 2009-11-07 Frederic Daigne , Robert Mochkovitch

The light curves of Gamma-Ray Bursts (GRBs) are believed to result from internal shocks reflecting the activity of the GRB central engine. Their temporal deconvolution can reveal potential differences in the properties of the central…

The prompt emission of Gamma Ray Bursts extends from the early pulses observed in gamma-rays (>15 keV) to very late flares of X-ray photons (0.3-10 keV). The duration of prompt gamma-ray pulses is rather constant while the width of X-ray…

High Energy Astrophysical Phenomena · Physics 2018-08-01 A. Pescalli , M. Ronchi , G. Ghirlanda , G. Ghisellini

Radiation-mediated shocks (RMSs) occurring below the photosphere in a gamma-ray burst (GRB) jet could play a crucial role in shaping the prompt emission. In this paper, we study the time-resolved signal expected from such early shocks. We…

High Energy Astrophysical Phenomena · Physics 2026-05-21 Filip Alamaa , Frédéric Daigne

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

We analyze gamma-ray bursts (GRBs) detected by \textit{Fermi}/Gamma-Ray Burst Monitor (GBM) and having single pulse. We fit the light curves with a model having exponential rise and decay parts. We perform a detailed time-resolved…

High Energy Astrophysical Phenomena · Physics 2015-06-19 Rupal Basak , A. R. Rao

We find and study a variety of the spectral-temporal behavior during the decay phase of long and bright GRB pulses. Even though only a small fraction of observed bursts exhibit such pulses, these are of interest to study as they reflect…

Astrophysics · Physics 2009-11-07 Felix Ryde , Roland Svensson

We analyze the spectral evolution of 62 bright Fermi gamma-ray bursts with large enough signal to noise to allow for time resolved spectral analysis. We develop a new algorithm to test for single-pulse morphology that is insensitive to the…

High Energy Astrophysical Phenomena · Physics 2024-08-28 Ian Busby , Davide Lazzati

To understand the physical mechanisms underlying the prompt emission of gamma-ray bursts (GRB), single FRED (Fast-Rise-Exponential-Decay) profile GRBs serve as an ideal sample, as they origin from single epoch central engine activity. These…

High Energy Astrophysical Phenomena · Physics 2026-03-24 Shu-Xu Yi , Chen-Wei Wang , Shao-Lin Xiong , Shuang-Nan Zhang , Romain Maccary , Rahim Moradi , Shuo Xiao , Hua Feng

Gamma-ray bursts (GRBs) exhibit a diversity of spectra. Several spectral models (e.g., Band, cutoff power-law, and blackbody) and their hybrid versions (e.g., Band+blackbody) have been widely used to fit the observed GRB spectra. Here, we…

High Energy Astrophysical Phenomena · Physics 2023-06-14 Liang Li

Several patterns have been discovered in how some spectral characteristics change during the decaying phase of long (> few s.) GRB pulses. We compare these observed signatures with those expected from a relativistically expanding shell.…

Astrophysics · Physics 2009-11-07 Felix Ryde , Vahe Petrosian