Shear Particle Acceleration in Structured Gamma-Ray Burst Jets. II. Viewing Angle Effect on the Prompt Emission and Application to GRB 170817A
Multimessenger observations suggest that the gamma-ray burst on 2017 August 17 (GRB 170817A) resulted from off-axial observations of its structured jet, which consists of a narrow ultrarelativistic jet core surrounded by a wide mild-relativistic cocoon. In a serious paper, we explore the emission of...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/1538-4357/adb722 |
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| Summary: | Multimessenger observations suggest that the gamma-ray burst on 2017 August 17 (GRB 170817A) resulted from off-axial observations of its structured jet, which consists of a narrow ultrarelativistic jet core surrounded by a wide mild-relativistic cocoon. In a serious paper, we explore the emission of shear-accelerated electrons in the mixed jet-cocoon region in a series of papers. This paper focuses on the viewing angle effect for a structured jet by considering the emission from the shear-accelerated electrons. It is found that the observed synchrotron (Syn) emission peaks at the infrared band and the Syn self-Compton emission peaks at the band of hundreds of keV. They are not sensitive to the viewing angle. In the off-axis observations scenario, the prompt emission spectrum is dominated by the emission of the shear-accelerated electrons. The prompt gamma-ray spectrum of GRB 170817A can be well explained with our model by setting the velocity of the inner edge of the cocoon region as 0.9 c , the magnetic field strength as 21 G, the injected initial electron Lorentz factor as 10 ^3 , and the viewing angle as 0.44 rad. We argue that the joint observations in the infrared/optical and X-ray bands are critical to verify our model. |
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| ISSN: | 1538-4357 |