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Article

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

by 1,* and 2,3
1
Department of Astronomy, School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
2
Department of Astronomy, University of Science and Technology of China, Hefei 230026, China
3
School of Astronomy and Space Science, Nanjing University, Nanjing 210023, China
*
Author to whom correspondence should be addressed.
Academic Editors: Elena Moretti and Francesco Longo
Galaxies 2021, 9(3), 68; https://doi.org/10.3390/galaxies9030068
Received: 30 July 2021 / Revised: 9 September 2021 / Accepted: 13 September 2021 / Published: 15 September 2021
(This article belongs to the Special Issue Gamma-Ray Burst Science in 2030)
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 α1.5 predicted by the synchrotron radiation is inconsistent with the observed value α1. 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 Bt1, 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. View Full-Text
Keywords: gamma rays bursts; radiation mechanisms; non-thermal gamma rays bursts; radiation mechanisms; non-thermal
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MDPI and ACS Style

Wang, K.; Dai, Z.-G. The Low-Energy Spectral Index of Gamma-ray Burst Prompt Emission from Internal Shocks. Galaxies 2021, 9, 68. https://doi.org/10.3390/galaxies9030068

AMA Style

Wang K, Dai Z-G. The Low-Energy Spectral Index of Gamma-ray Burst Prompt Emission from Internal Shocks. Galaxies. 2021; 9(3):68. https://doi.org/10.3390/galaxies9030068

Chicago/Turabian Style

Wang, Kai, and Zi-Gao Dai. 2021. "The Low-Energy Spectral Index of Gamma-ray Burst Prompt Emission from Internal Shocks" Galaxies 9, no. 3: 68. https://doi.org/10.3390/galaxies9030068

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