Hao, Jing-Meng 2013 短暴的delay time

主要内容:
通过对delay time的分布来限制短暴的前身星。

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Title:		Progenitor delay-time distribution of short gamma-ray bursts: Constraints from observations
Authors:		Hao, Jing-Meng; Yuan, Ye-Fei
Affiliation:		AA(Key Laboratory for Research in Galaxies and Cosmology CAS, Department of Astronomy, University of Science and Technology of China Hefei, Anhui, 230026, PR China yfyuan@ustc.edu.cn), AB(Key Laboratory for Research in Galaxies and Cosmology CAS, Department of Astronomy, University of Science and Technology of China Hefei, Anhui, 230026, PR China)
Publication:		Astronomy & Astrophysics, Volume 558, id.A22, 6 pp. (A&A Homepage)
Publication Date:		10/2013
Origin:		EDP Sciences
Astronomy Keywords:		gamma-ray burst: general, binaries: close, stars: evolution, stars: formation, stars: neutron, black hole physics
DOI:		10.1051/0004-6361/201321471
Bibliographic Code:		2013A&A...558A..22H

Abstract

Context. The progenitors of short gamma-ray bursts (SGRBs) have not yet been well identified. The most popular model is the merger of compact object binaries (NS-NS/NS-BH). However, other progenitor models cannot be ruled out. The delay-time distribution of SGRB progenitors, which is an important property to constrain progenitor models, is still poorly understood.
Aims: We aim to better constrain the luminosity function of SGRBs and the delay-time distribution of their progenitors with newly discovered SGRBs.
Methods: We present a low-contamination sample of 16 Swift SGRBs that is better defined by a duration shorter than 0.8 s. By using this robust sample and by combining a self-consistent star formation model with various models for the distribution of time delays, the redshift distribution of SGRBs is calculated and then compared to the observational data.
Results: We find that the power-law delay distribution model is disfavored and that only the lognormal delay distribution model with the typical delay τ ≳ 3 Gyr is consistent with the data. Comparing Swift SGRBs with T₉₀ > 0.8 s to our robust sample (T₉₀ < 0.8 s), we find a significant difference in the time delays between these two samples.
Conclusions: Our results show that the progenitors of SGRBs are dominated by relatively long-lived systems (τ ≳ 3 Gyr), which contrasts the results found for Type Ia supernovae. We therefore conclude that primordial NS-NS systems are not favored as the dominant SGRB progenitors. Alternatively, dynamically formed NS-NS/BH and primordial NS-BH systems with average delays longer than 5 Gyr may contribute a significant fraction to the overall SGRB progenitors.

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