NDLI: The Low-Energy Spectral Index of Gamma-ray Burst Prompt Emission from Internal Shocks

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The Low-Energy Spectral Index of Gamma-ray Burst Prompt Emission from Internal Shocks

Content Provider	MDPI
Author	Wang, Kai Dai, Zi-Gao
Copyright Year	2021
Abstract	The prompt emission of most gamma-ray bursts (GRBs) typically exhibits a non-thermal Band component. The synchrotron radiation in the popular internal shock model is generally put forward to explain such a non-thermal component. However, the low-energy photon index $α \sim - 1.5$ predicted by the synchrotron radiation is inconsistent with the observed value $α \sim - 1$ . Here, we investigate the evolution of a magnetic field during propagation of internal shocks within an ultrarelativistic outflow, and revisit the fast cooling of shock-accelerated electrons via synchrotron radiation for this evolutional magnetic field. We find that the magnetic field is first nearly constant and then decays as $B^{'} \propto t^{- 1}$ , which leads to a reasonable range of the low-energy photon index, $- 3 / 2 < α < - 2 / 3$ . In addition, if a rising electron injection rate during a GRB is introduced, we find that $α$ reaches $- 2 / 3$ more easily. We thus fit the prompt emission spectra of GRB 080916c and GRB 080825c.
Starting Page	68
e-ISSN	20754434
DOI	10.3390/galaxies9030068
Journal	Galaxies
Issue Number	3
Volume Number	9
Language	English
Publisher	MDPI
Publisher Date	2021-09-15
Access Restriction	Open
Subject Keyword	Galaxies Astronomy and Astrophysics Gamma Rays Bursts Radiation Mechanisms Non-thermal
Content Type	Text
Resource Type	Article

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