High energy emission of GRB 130821A: constraining the density profile of the circum-burst medium as well as the initial Lorentz factor of the outflow

Abstract

GRB 130821A was detected by Fermi-GBM/LAT, Konus-Wind, SPI-ACS/INTEGRAL, RHESSI and Mars Odyssey-HEND. Although the data of GRB 130821A are very limited, we show in this work that the high energy gamma-ray emission (i.e., above 100 MeV) alone imposes tight constraint on the density profile of the circum-burst medium as well as the initial Lorentz factor of the outflow. The temporal behavior of the high energy gamma-ray emission is consistent with the forward shock synchrotron radiation model and the circum-burst medium likely has a constant-density profile. The Lorentz factor is about a few hundred, similar to other bright GRBs.

7 pages, 4 figures, 2 tables, ApJ, in press

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Cited by in corpus (4)

• The 7.2/3 Years Collection of Well-Monitored Fermi-LAT GRB Afterglows
• GRB 131231A: Implications of the GeV emission
• Origin for the Prompt Spectral Evolution Characteristics and High Energy Emission during the X-Ray Flare in GRB 180720B
• Jets in a Gamma-Ray Burst During its Prompt Emission: Evolution of Lorentz Factor