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A five-parameter expression for a smoothly broken power law is presented. It is used to fit Gamma-Ray Burst (GRB) spectra observed by BATSE. The function is compared to previously used four-parameter functions, such as a sharply broken…

Astrophysics · Physics 2007-05-23 Felix Ryde

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

A Band function has become the standard spectral function used to describe the prompt emission spectra of gamma-ray bursts (GRBs). However, deviations from this function have previously been observed in GRBs detected by BATSE and in…

The \emph{Swift} Burst Alert Telescope (BAT), operating in the 15--150 keV energy band, struggles to detect the peak energy ($E_{\rm p}$) of gamma-ray bursts (GRBs), as most GRBs have $E_{\rm p}$ values typically distributed between 200-300…

High Energy Astrophysical Phenomena · Physics 2024-12-12 Liang Li , Yu Wang

Gamma-ray Bursts (GRBs) prompt emission spectra are often fitted with the empirical ''Band" function, namely two power laws smoothly connected. The typical slope of the low energy (sub-MeV) power law is $\alpha_{B}\simeq -1$. In a small…

High Energy Astrophysical Phenomena · Physics 2021-08-25 M. Toffano , G. Ghirlanda , L. Nava , G. Ghisellini , M. E. Ravasio , G. Oganesyan

The spectra of gamma-ray bursts (GRBs) in a wide energy range can usually be well described by the Band function, which is a two smoothly jointed power laws cutting at a breaking energy. Below the breaking energy, the Band function reduces…

High Energy Astrophysical Phenomena · Physics 2016-06-08 Hai-Nan Lin , Xin Li , Zhe Chang

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

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 radiative process responsible for gamma-Ray Burst (GRB) prompt emission has not been identified yet. If dominated by fast-cooling synchrotron radiation, the part of the spectrum immediately below the $\nu F_\nu$ peak energy should…

High Energy Astrophysical Phenomena · Physics 2017-09-20 Gor Oganesyan , Lara Nava , Giancarlo Ghirlanda , Annalisa Celotti

We statistically examine the gamma-ray burst (GRB) photon indices obtained by the Fermi-GBM and Fermi-LAT observations and compare the LAT GRB photon indices to the GBM GRB photon indices. We apply the jitter radiation to explain the GRB…

High Energy Astrophysical Phenomena · Physics 2020-07-29 Jirong Mao , Liande Li , Jiancheng Wang

In this paper, we continue to build support for the proposal to use gamma-ray bursts (GRBs) as standard candles in constructing the Hubble Diagram at redshifts beyond the current reach of Type Ia supernova observations. We confirm that…

High Energy Astrophysical Phenomena · Physics 2015-06-12 Jun-Jie Wei , Xue-Feng Wu , Fulvio Melia

Gamma Ray Bursts (GRBs) show evidence of different light curves, duration, afterglows, host galaxies and they explode within a wide redshift range. However, their spectral energy distributions (SEDs) appear to be very similar showing a…

High Energy Astrophysical Phenomena · Physics 2015-05-18 F. Massaro , J. E. Grindlay , A. Paggi

The use of GRB energetics for cosmography has long been advanced as a means to probe out to high redshifts, to the epoch of deceleration. However, the prompt energy release in GRBs, even when corrected for jetting geometry, is far from…

Astrophysics · Physics 2009-11-10 Andrew S. Friedman , Joshua S. Bloom

The prompt emission spectrum of Gamma-ray bursts (GRB) is characterized by a smoothly joint broken power-law spectrum known as the Band function. The typical low-energy photon index is $\sim -1$, which poses challenge to the standard…

High Energy Astrophysical Phenomena · Physics 2018-02-07 Siyao Xu , Yuan-Pei Yang , Bing Zhang

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 discuss the prompt emission of Gamma-Ray Bursts in different spectral energy bands. First, we suggest that a three-part synchrotron emission model is a good description of the ~20 keV - 1 MeV gamma-ray emission of GRBs. We show that this…

Astrophysics · Physics 2009-11-07 Nicole M. Lloyd-Ronning

The principal paradigm for gamma-ray bursts (GRBs) suggests that the prompt transient gamma-ray signal arises from multiple shocks internal to the relativistic expansion. This paper explores how GRB prompt emission spectra can constrain…

High Energy Astrophysical Phenomena · Physics 2009-06-25 Matthew G. Baring

We explore fitting gamma-ray burst spectra with three physically-motivated models, and thus revisit the viability of synchrotron radiation as the primary source of GRB prompt emission. We pick a sample of 100 bright GRBs observed by the…

High Energy Astrophysical Phenomena · Physics 2023-11-23 Suraj Poolakkil , Robert Preece , Peter Veres

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

Gamma Ray Bursts (GRBs) show evidence of different light curves, duration, afterglows, host galaxies and they explode within a wide redshift range. However, their spectral energy distributions (SEDs) appear to be very similar showing a…

High Energy Astrophysical Phenomena · Physics 2015-05-27 F. Massaro , J. E. Grindlay
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