An off-axis jet model for GRB 980425 and low-energy gamma-ray bursts

Astrophysical Journal Letters Volume 594 Issue 2 Page 2003-10 published_at 2003-09
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Title ( eng )
An off-axis jet model for GRB 980425 and low-energy gamma-ray bursts
Creator
Yamazaki Ryo
Yonetoku Daisuke
Nakamura Takashi
Source Title
Astrophysical Journal Letters
Volume 594
Issue 2
Start Page 2003
End Page 10
Abstract
Using a simple off-axis jet model of gamma-ray bursts (GRBs), we can reproduce the observed unusual properties of the prompt emission of GRB 980425, such as the extremely low isotropic equivalent γ-ray energy, the low peak energy, the high fluence ratio, and the long spectral lag when the jet with the standard energy of ∼1051 ergs and the opening half-angle of 10&j0; ≲ Δ&thetas; ≲ 30&j0; is seen from the off-axis viewing angle &thetas;v ∼ Δ&thetas; + 10γ-1, where γ is a Lorentz factor of the jet. For our adopted fiducial parameters, if the jet that caused GRB 980425 is viewed from the on-axis direction, the intrinsic peak energy Ep(1 + z) is ∼2.0–4.0 MeV, which corresponds to those of GRB 990123 and GRB 021004. We also discuss the connection of GRB 980425 in our model with the X-ray flash, and the origin of a class of GRBs with small Eγ.
Keywords
gamma rays
bursts
theory
NDC
Earth sciences. Geology [ 450 ]
Language
eng
Resource Type journal article
Publisher
University of Chicago Press
Date of Issued 2003-09
Rights
Copyright (c) 2003 The American Astronomical Society
Publish Type Version of Record
Access Rights open access
Source Identifier
[ISSN] 0004-637X
[DOI] 10.1086/378736
[DOI] http://dx.doi.org/10.1086/378736