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Information on the spectral shape of prompt emission in gamma-ray bursts (GRB) is mostly available only at energies $\gtrsim10$ keV, where the main instruments for GRB detection are sensitive. The origin of this emission is still very…

High Energy Astrophysical Phenomena · Physics 2019-08-14 Gor Oganesyan , Lara Nava , Giancarlo Ghirlanda , Andrea Melandri , Annalisa Celotti

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

Previous studies have considered synchrotron as the emission mechanism for prompt Gamma-Ray Bursts (GRBs). These works have shown that the electrons must cool on a timescale comparable to the dynamic time at the source in order to satisfy…

High Energy Astrophysical Phenomena · Physics 2018-02-28 Paz Beniamini , Rodolfo Barniol Duran , Dimitrios Giannios

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

(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

The origin of prompt emission in $\gamma$-ray bursts (GRBs) is highly debated topic. The observed spectra are supposed to play a crucial role in constraining the location of the emitting region, the strength of the magnetic field and the…

High Energy Astrophysical Phenomena · Physics 2020-06-26 Gor Oganesyan

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

A substantial fraction of prompt GRB spectra have soft spectral indexes exceeding the maximum allowed by the synchrotron model alpha_{max}=-2/3. Some spectra also exhibit very sharp break at E_p, inconsistent with the smooth synchrotron…

Astrophysics · Physics 2009-11-10 Mikhail V. Medvedev

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

Synchrotron radiation from accelerated electrons above the photosphere of a relativistic ejecta is a natural candidate for the dominant process for the prompt GRB emission. There is however a tension between the predicted low-energy…

High Energy Astrophysical Phenomena · Physics 2025-01-29 Frédéric Daigne , Željka Bošnjak

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

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 reexamine the general synchrotron model for GRBs' prompt emission and determine the regime in the parameter phase space in which it is viable. We characterize a typical GRB pulse in terms of its peak energy, peak flux and duration and…

High Energy Astrophysical Phenomena · Physics 2015-06-12 Paz Beniamini , Tsvi Piran

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 investigate neutrino emission from gamma-ray bursts (GRBs) under alternative scenarios for prompt emission (the photospheric and synchrotron self-Compton scenarios) rather than the classical optically thin synchrotron scenario. In the…

Astrophysics · Physics 2019-01-14 Kohta Murase

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 explore a one-zone hadronic model that may be able to reproduce $\gamma$-ray burst (GRB) prompt emission with a minimum of free parameters. Assuming only that GRBs are efficient high-energy proton accelerators and without the presence of…

High Energy Astrophysical Phenomena · Physics 2015-06-22 Maria Petropoulou , Stavros Dimitrakoudis , Apostolos Mastichiadis , Dimitrios Giannios

For over two decades, gamma-ray burst (GRB) prompt emission spectra were modelled with smoothly-broken power laws (Band function), and a positive and tight correlation between the spectral rest-frame peak energy $E_p$ and the total…

High Energy Astrophysical Phenomena · Physics 2024-09-16 Alessio Mei , Gor Oganesyan , Samanta Macera

Even though the observed spectra for GRB prompt emission is well constrained, no single radiation mechanism can robustly explain its distinct non-thermal nature. Here we explore the radiation mechanism with the photospheric emission model…

High Energy Astrophysical Phenomena · Physics 2020-08-10 Mukul Bhattacharya , Pawan Kumar

Although the observed spectra for gamma-ray burst (GRB) prompt emission is well constrained, the underlying radiation mechanism is still not very well understood. We explore photospheric emission in GRB jets by modelling the Comptonization…

High Energy Astrophysical Phenomena · Physics 2021-10-29 Mukul Bhattacharya , Pawan Kumar
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