Feng 2010 拟合三个高能暴的辐射

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GRBs 080916C, 090902B, and 090926A

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Title:		Multiband Fitting to Three Long GRBs with Fermi/LAT Data: Structured Ejecta Sweeping up a Density-Jump Medium
Authors:		Feng, S. Y.; Dai, Z. G.
Publication:		eprint arXiv:1011.3103
Publication Date:		11/2010
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Bibliographic Code:		2010arXiv1011.3103F

Abstract

We present broadband (radio, optical, X-ray and GeV) fits to the afterglow light curves and spectra of three long-duration gamma-ray bursts (GRBs 080916C, 090902B, and 090926A) detected by the Gamma-Ray Burst Monitor (GBM) and Large Area Telescope (LAT) instruments on the Fermi satellite. Using the observed broadband data, we study the origin of the high energy emission, and suggest that the early-time GeV emission and the late-time radio, optical, and X-ray afterglows can be understood as being due to synchrotron emission from an external forward shock caused by structured ejecta propagating in a wind bubble jumping to a homogeneous density medium. The structured ejecta can well explain the early rising feature of the GeV emission from these bursts and the density-jump medium can account for some certain plateaus or flares in the late afterglows. From our fits, we find that these Fermi-LAT events preferentially occur in a low-density circumburst environment, in which case the Klein-Nishina cutoff effect is significant. Such an environment might result from superbubbles or low-metallicity progenitor stars (which have a low mass-loss rate at late times of stellar evolution) of type Ib/c supernovae.

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