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We report results of a systematic study of the broad--band (2--2000 keV) time--resolved prompt emission spectra of a sample of Gamma-Ray Bursts (GRBs) detected with both the Wide Field Cameras (WFCs) aboard the BeppoSAX satellite and the…

High Energy Astrophysical Phenomena · Physics 2015-06-17 Filippo Frontera , Lorenzo Amati , Ruben Farinelli , Simone Dichiara , Cristiano Guidorzi , Raffaella Landi , Lev Titarchuk

While the Band function or other phenomenological functions are commonly used to fit GRB prompt emission spectra, we propose a new parametric function that is inspired by an internal shock physical model. We use this function as a proxy of…

High Energy Astrophysical Phenomena · Physics 2020-08-19 M. Yassine , F. Piron , F. Daigne , R. Mochkovitch , F. Longo , N. Omodei , G. Vianello

The prompt phase X- and $\gamma$-ray light curves of gamma-ray bursts (GRBs) exhibit erratic and complex behaviour, often with multiple pulses. The temporal shape of individual pulses is often modelled as 'fast rise exponential decay'…

High Energy Astrophysical Phenomena · Physics 2025-07-14 A Gowri , A. Pe'er , F. Ryde , H. Dereli-Bégué

The prompt emission spectra of gamma-ray bursts (GRBs) usually have a dominant component that is well described by a phenomenological "Band" function. The physical origin of this spectral component is debated. Although the traditional…

High Energy Astrophysical Phenomena · Physics 2015-06-11 Bing Zhang , Rui-Jing Lu , En-Wei Liang , Xue-Feng Wu

The recent launches of the Einstein Probe (EP) and the Space Variable Objects Monitor (SVOM) mission have led to the detection of a growing number of long GRBs with significant, early soft X-ray flux during their gamma-ray emission,…

High Energy Astrophysical Phenomena · Physics 2025-10-21 Ziming Wang , Chenyu Wang , He Gao , Hua Feng , An Li , Lin Lin , Songyu Shen

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

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

It has been suggested that the prompt emission in gamma-ray bursts consists of several components giving rise to the observed spectral shape. Here we examine a sample of the 8 brightest, single pulsed {\it Fermi} bursts whose spectra are…

High Energy Astrophysical Phenomena · Physics 2016-01-27 S. Iyyani , F. Ryde , J. M. Burgess , A. Pe'er , D. B\' egué

Aims. With the accumulation of polarization data in the gamma-ray burst (GRB) prompt phase, polarization models can be tested. Methods. We predicted the time-integrated polarizations of 37 GRBs with polarization observation. We used their…

High Energy Astrophysical Phenomena · Physics 2023-02-22 R. Y. Guan , M. X. Lan

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 long-lasting tension between the observed spectra of gamma ray bursts (GRBs) and the predicted synchrotron emission spectrum might be solved if electrons do not completely cool. Evidence for incomplete cooling was recently found in…

High Energy Astrophysical Phenomena · Physics 2019-05-15 M. E. Ravasio , G. Ghirlanda , L. Nava , G. Ghisellini

The emission mechanism during the prompt phase in gamma-ray bursts (GRBs) can be investigated through correlations between spectral properties. Here, we revisit the correlation relating the instantaneous flux, $F$, and the photon index…

High Energy Astrophysical Phenomena · Physics 2019-01-16 Felix Ryde , Hoi-Fung Yu , Hüsne Dereli-Bégué , Christoffer Lundman , Asaf Pe'er , Liang Li

The radiation mechanism of the prompt emission of gamma-ray bursts (GRBs) remains an open question. Although their spectra are usually well fitted with the empirical Band function, which is widely believed to be fully non-thermal and…

High Energy Astrophysical Phenomena · Physics 2018-10-17 Shu-Jin Hou , Bin-Bin Zhang , Yan-Zhi Meng , Xue-Feng Wu , En-Wei Liang , Hou-Jun Lü , Tong Liu , Yun-Feng Liang , Lin Lin , Rui-jing Lu , Jin-Shu Huang , Bing Zhang

Gamma-ray bursts (GRBs) show different behaviours and trends in their spectral evolution. One of the methods used to understand the physical origin of these behaviours is to study correlation between the spectral fit parameters. In this…

High Energy Astrophysical Phenomena · Physics 2020-06-09 Hüsne Dereli Bégué , Hoi-Fung Yu , Felix Ryde

We aim to obtain a measure of the curvature of time-resolved spectra that can be compared directly to theory. This tests the ability of models such as synchrotron emission to explain the peaks or breaks of GBM prompt emission spectra. We…

We discuss the new surprising observational results that indicate quite convincingly that the prompt emission of Gamma-Ray Bursts (GRBs) is due to synchrotron radiation produced by a particle distribution that has a low energy cut-off. The…

High Energy Astrophysical Phenomena · Physics 2020-04-29 G. Ghisellini , G. Ghirlanda , G. Oganesyan , S. Ascenzi , L. Nava , A. Celotti , O. S. Salafia , E. M. Ravasio , M. Ronchi

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 observations of the prompt emission of gamma ray bursts (GRB) by GLAST Burst Monitor (GBM), on board Fermi Gamma-ray Space Telescope, suggest the presence of a significant thermal spectral component, whose origin is not well understood.…

High Energy Astrophysical Phenomena · Physics 2017-03-29 Priya Bharali , Sunder Sahayanathan , Ranjeev Misra , Kalyanee Boruah

The mechanism that causes the prompt-emission episode of gamma-ray bursts (GRBs) is still widely debated despite there being thousands of prompt detections. The favoured internal shock model relates this emission to synchrotron radiation.…

After more than 40 years from their discovery, the long-lasting tension between predictions and observations of GRBs prompt emission spectra starts to be solved. We found that the observed spectra can be produced by the synchrotron process,…

High Energy Astrophysical Phenomena · Physics 2020-03-25 Maria Edvige Ravasio