Virgili 2009 很大一部分短暴可能不是来自于双致密星并合

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Title:		Are all short-hard gamma-ray bursts produced from mergers of compact stellar objects?
Authors:		Virgili, Francisco J.; Zhang, Bing; O'Brien, Paul; Troja, Eleonora
Publication:		eprint arXiv:0909.1850
Publication Date:		09/2009
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		ApJ, submitted
Bibliographic Code:		2009arXiv0909.1850V

Abstract

Abridged: The origin and progenitors of short-hard gamma-ray bursts remain a puzzle and a highly debated topic. The most popular model to interpret short-hard bursts is the merger of two compact stellar objects (NS-NS or NS-BH). A closer analysis by Zhang et al. reveals that a small sample of GRBs that have the most robust evidence of the compact star merger origin (Type I) is not a fair representation of the BATSE short-hard GRB sample. This raises the question whether all short-hard GRBs are Type I, and whether there is a strong contamination of GRBs due to massive star core collapses (Type II) in the short-hard GRB sample. We utilize a Monte Carlo approach to determine whether a merger progenitor model can self-consistently account for all the observations of short-hard GRBs, including a sample with redshift measurements in the Swift era (z-known sample) and the CGRO/BATSE sample. We apply various merger time delay distributions invoked in compact star merger models to derive the redshift distributions of Type I GRBs, and then constrain the unknown luminosity function of Type I GRBs. We find that it is difficult to reconcile a merger scenario progenitor with all the data. In order to satisfy both observational constraints, the allowed merger delay time scale is essentially zero, which suggests that most short GRBs should follow the star forming history of the universe. We explore the possibility that the observed short-hard GRB sample is a mix of Type I (which requires a merger time delay to define the z-distribution) and Type II (whose z-distribution tracks the star forming rate) GRBs. We conclude that Type I GRBs only account for a small fraction of short-hard GRBs and that the majority of short-hard GRBs track the star forming history of the universe and are likely of Type II origin.

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