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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

It has been suggested that the prompt emission in gamma-ray bursts (GRBs) could be described by radiation from the photosphere in a hot fireball. Such models must be tested by directly fitting them to data. In this work we use data from the…

High Energy Astrophysical Phenomena · Physics 2019-01-30 Björn Ahlgren , Josefin Larsson , Erik Ahlberg , Christoffer Lundman , Felix Ryde , Asaf Pe'er

The origin of prompt emission from gamma ray bursts remains to be an open question. Correlated prompt optical and gamma-ray emission observed in a handful of GRBs strongly suggests a common emission region, but failure to adequately fit the…

High Energy Astrophysical Phenomena · Physics 2016-12-21 S. Guiriec , C. Kouveliotou , D. H. Hartmann , J. Granot , K. Asano , P. Meszaros , R. Gill , N. Gehrels , J. McEnery

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

The origin of gamma-ray burst (GRB) prompt emission, bursts of gamma-rays lasting from shorter than one second to thousands of seconds, remains not fully understood after more than 40 years of observations. The uncertainties lie in several…

High Energy Astrophysical Phenomena · Physics 2014-03-03 Bing Zhang

The emission from a gamma-ray burst (GRB) photosphere can give rise to a variety of spectral shapes. The spectrum can retain the shape of a Planck function or it can be broadened and have the shape of a Band function. This fact is best…

Among the more than 1000 gamma-ray bursts observed by the Fermi Gamma-ray Space Telescope, a large fraction show narrow and hard spectra inconsistent with non-thermal emission, signifying optically thick emission from the photosphere.…

High Energy Astrophysical Phenomena · Physics 2019-08-14 M. Axelsson

We analyze the spectral evolution of GRB 090902B and show that subphotospheric dissipation can explain both the spectra and the spectral evolution. The emission from a GRB photosphere can give rise to a variety of spectral shapes. The…

High Energy Astrophysical Phenomena · Physics 2011-11-03 T. Nymark , M. Axelsson , C. Lundman , E. Moretti , F. Ryde , A. Pe'er

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…

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

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

Radially inhomogeneous gamma-ray burst (GRB) jets release variable photospheric emission and can have internal shocks occurring above the photosphere. We generically formulate a photospheric emission model of GRBs including Compton…

High Energy Astrophysical Phenomena · Physics 2015-05-18 Kenji Toma , Xue-Feng Wu , Peter Meszaros

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

We propose a model for the spectral formation of Gamma Ray Burst (GRB) prompt emission, where the phenomenological Band's function is usually applied to describe the GRB prompt emission. We suggest that the GRB prompt emission is mainly a…

High Energy Astrophysical Phenomena · Physics 2015-06-04 Lev Titarchuk , Ruben Farinelli , Filippo Frontera , Lorenzo Amati

Photospheric (thermal) emission is inherent to the gamma-ray burst (GRB) "fireball" model. We show here, that inclusion of this component in the analysis of the GRB prompt emission phase naturally explains some of the prompt GRB spectra…

High Energy Astrophysical Phenomena · Physics 2015-05-19 Asaf Pe'er , Bin-Bin Zhang , Felix Ryde , Sinéad McGlynn , Bing Zhang , Robert D. Preece , Chryssa Kouveliotou

The MeV spectral peak of gamma-ray bursts (GRBs) is best explained as photospheric emission from a dissipative relativistic jet. The observed non-blackbody spectrum shows that sub-photospheric dissipation involves both thermal plasma…

High Energy Astrophysical Phenomena · Physics 2016-11-07 Christoffer Lundman , Indrek Vurm , Andrei M. Beloborodov

The photospheric emission in the prompt phase is the natural prediction of the original fireball model for gamma-ray burst (GRB) due to the large optical depth ($\tau >1$) at the base of the outflow, which is supported by the quasi-thermal…

High Energy Astrophysical Phenomena · Physics 2021-12-02 Yan-Zhi Meng , Jin-Jun Geng , Xue-Feng Wu

The prompt $\gamma$-rays of gamma-ray bursts (GRBs) may originate from the photosphere of a relativistic jet. However, only a few GRBs have been observed with evident blackbody-like emission, for example, GRB~090902B. It has been…

High Energy Astrophysical Phenomena · Physics 2025-07-22 Guo-Yu Li , Da-Bin Lin , Zhi-Lin Chen , En-Wei Liang

Modeling of gamma-ray burst (GRB) prompt emission spectra sometimes requires a (quasi-) thermal spectral component in addition to the Band function. In photospheric emission models, a prominent thermal component broadened by…

High Energy Astrophysical Phenomena · Physics 2020-09-30 Ramandeep Gill , Jonathan Granot , Paz Beniamini

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
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