Quasi-thermal Photosphere Emission from Structured Jets of Gamma-Ray Bursts

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Hauptverfasser: Hu, Ding-Fang, Geng, Jin-Jun, Gao, Hao-Xuan, Yan, Jing-Zhi, Wu, Xue-Feng
Format: Preprint
Veröffentlicht: 2025
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author Hu, Ding-Fang
Geng, Jin-Jun
Gao, Hao-Xuan
Yan, Jing-Zhi
Wu, Xue-Feng
author_facet Hu, Ding-Fang
Geng, Jin-Jun
Gao, Hao-Xuan
Yan, Jing-Zhi
Wu, Xue-Feng
contents The prompt emission of gamma-ray bursts (GRBs) is supposed to be released from the relativistic jet launched from the central engine. Apart from the non-thermal nature of the spectra in a majority of GRBs, there is evidence for the presence of quasi-thermal components in the prompt emission of a few GRBs according to observations by Fermi satellite. On the other hand, the GRB jet has been revealed as structured in recent research. The theoretical observed spectra of photosphere emissions by an off-axis observer and the dependence of the spectra on the viewing angle under the assumption of structured jets remain unexplored. In this paper, we numerically calculate the instantaneous photosphere spectra by different viewing angles from a structured jet, from which relevant temporal and spectral characteristics are derived. Moreover, we address the necessity of proper treatment of the outflow boundary in the photosphere emission scenario. Furthermore, our calculations suggest that the Einstein Probe and Space-based multi-band astronomical Variable Object Monitor will have the capability to detect the short GRBs similar to GRB 170817A up to a luminosity distance of 200Mpc if the off-axis viewing angle is less than 10 degrees.
format Preprint
id arxiv_https___arxiv_org_abs_2504_15011
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Quasi-thermal Photosphere Emission from Structured Jets of Gamma-Ray Bursts
Hu, Ding-Fang
Geng, Jin-Jun
Gao, Hao-Xuan
Yan, Jing-Zhi
Wu, Xue-Feng
High Energy Astrophysical Phenomena
The prompt emission of gamma-ray bursts (GRBs) is supposed to be released from the relativistic jet launched from the central engine. Apart from the non-thermal nature of the spectra in a majority of GRBs, there is evidence for the presence of quasi-thermal components in the prompt emission of a few GRBs according to observations by Fermi satellite. On the other hand, the GRB jet has been revealed as structured in recent research. The theoretical observed spectra of photosphere emissions by an off-axis observer and the dependence of the spectra on the viewing angle under the assumption of structured jets remain unexplored. In this paper, we numerically calculate the instantaneous photosphere spectra by different viewing angles from a structured jet, from which relevant temporal and spectral characteristics are derived. Moreover, we address the necessity of proper treatment of the outflow boundary in the photosphere emission scenario. Furthermore, our calculations suggest that the Einstein Probe and Space-based multi-band astronomical Variable Object Monitor will have the capability to detect the short GRBs similar to GRB 170817A up to a luminosity distance of 200Mpc if the off-axis viewing angle is less than 10 degrees.
title Quasi-thermal Photosphere Emission from Structured Jets of Gamma-Ray Bursts
topic High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2504.15011