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The debate regarding the emission mechanism in gamma-ray bursts has been long-standing. Here, we study the spectral signatures of photospheric emission, accounting for subphotospheric dissipation by a radiation-mediated shock. The shocks…

High Energy Astrophysical Phenomena · Physics 2024-07-15 Filip Alamaa , Felix Ryde , Christoffer Lundman

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

Gamma-ray burst (GRB) spectra are typically non-thermal, with many including two spectral breaks suggestive of optically-thin emission. However, the emitted spectrum from a GRB photosphere, which includes prior dissipation of energy by…

High Energy Astrophysical Phenomena · Physics 2025-12-16 Oscar Wistemar , Filip Alamaa , Felix Ryde

Internal shocks provide a plausible heating mechanism in the jets of gamma-ray bursts (GRBs). Shocks occurring below the jet photosphere are mediated by radiation. It was previously found that radiation mediated shocks (RMSs) inside GRB…

High Energy Astrophysical Phenomena · Physics 2019-07-17 Christoffer Lundman , Andrei Beloborodov

Modeling subphotospheric shocks in a gamma-ray burst (GRB) is challenging due to the various timescales that must be resolved, and the fact that the same radiation dynamically mediates the shocks while forming the observed signal. Here, we…

High Energy Astrophysical Phenomena · Physics 2026-04-10 Jona Nordin Nobuoka , Filip Alamaa , Felix Ryde , Christoffer Lundman

A shock that form below the photosphere of a GRB outflow is mediated by Compton scattering of radiation advected into the shock by the upstream fluid. The characteristic scale of such a shock, a few Thomson depths, is larger than any…

High Energy Astrophysical Phenomena · Physics 2015-06-05 Amir Levinson

A complete understanding of Gamma Ray Bursts (GRBs) has been difficult to achieve due to our incomplete knowledge of the radiation mechanism that is responsible for producing the prompt emission. This emission, which is detected in the…

High Energy Astrophysical Phenomena · Physics 2021-12-15 Tyler Parsotan , Davide Lazzati

Emission from the photosphere in gamma-ray burst (GRB) jets can be substantially affected by subphotospheric energy dissipation, which is typically caused by radiation-mediated shocks (RMSs). We study the observational characteristics of…

High Energy Astrophysical Phenomena · Physics 2023-10-25 Filip Samuelsson , Felix Ryde

While Gamma Ray Bursts (GRBs) have the potential to shed light on the astrophysics of jets, compact objects, and cosmology, a major set back in their use as probes of these phenomena stems from our incomplete knowledge surrounding their…

High Energy Astrophysical Phenomena · Physics 2024-08-12 Tyler Parsotan , Davide Lazzati

The study of Gamma Ray Bursts (GRBs) has the potential to improve our understanding of high energy astrophysical phenomena. In order to reliably use GRBs to this end, we first need to have a well-developed grasp of the mechanism that…

High Energy Astrophysical Phenomena · Physics 2021-10-26 Tyler Parsotan , Davide Lazzati

Discerning the radiative dissipation mechanism for prompt emission in Gamma-Ray Bursts (GRBs) requires detailed spectroscopic modeling that straddles the $\nu F_{\nu}$ peak in the 100 keV - 1 MeV range. Historically, empirical fits such as…

The origin of prompt emission in GRBs is not yet well understood. The simplest and most popular model is Synchrotron, Self-Compton (SSC) emission produced by internal shocks inside an ultra-relativistic jet. However, recent observations of…

Cosmology and Nongalactic Astrophysics · Physics 2015-03-17 Houri Ziaeepour , Brian Gardner

Internal shocks are a leading candidate for the dissipation mechanism that powers the prompt $\gamma$-ray emission in gamma-ray bursts (GRBs). In this scenario a compact central source produces an ultra-relativistic outflow with varying…

High Energy Astrophysical Phenomena · Physics 2023-12-25 Sk. Minhajur Rahaman , Jonathan Granot , Paz Beniamini

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

Sub-photospheric shock dissipation is one of the main proposed mechanisms for producing the prompt gamma-ray burst (GRB) emission. Such shocks are mediated by scattering of radiation. We introduce a time dependent, special relativistic code…

High Energy Astrophysical Phenomena · Physics 2018-05-02 Christoffer Lundman , Andrei Beloborodov , Indrek Vurm

We consider a model in which the ultra-relativistic jet in a gamma-ray burst (GRB) is cold and magnetically accelerated. We assume that the energy flux in the outflowing material is partially thermalized via internal shocks or a reverse…

High Energy Astrophysical Phenomena · Physics 2015-05-28 Ramesh Narayan , Pawan Kumar , Alexander Tchekhovskoy

Recent advances in fitting prompt emission spectra in gamma-ray bursts (GRBs) are boosting our understanding of the still elusive origin of this radiation. These progresses have been possible thanks to a more detailed analysis of the…

High Energy Astrophysical Phenomena · Physics 2018-02-07 Lara Nava , Gor Oganesyan , Maria E. Ravasio , Lorenzo Amati , Giancarlo Ghirlanda , Paul O'Brien , Julian P. Osborne , Richard Willingale

Although Gamma Ray Bursts (GRBs) have been detected for many decades, the lack of knowledge regarding the radiation mechanism that produces the energetic flash of radiation, or prompt emission, from these events has prevented the full use…

High Energy Astrophysical Phenomena · Physics 2022-02-23 Tyler Parsotan , Davide Lazzati

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

The jet photosphere has been proposed as the origin for the gamma-ray burst (GRB) prompt emission. In many such models, characteristic features in the spectra appear below the energy range of the $\textit{Fermi}$ GBM detectors, so joint…

High Energy Astrophysical Phenomena · Physics 2019-07-31 Björn Ahlgren , Josefin Larsson , Vlasta Valan , Daniel Mortlock , Felix Ryde , Asaf Pe'er
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