Zheng 2009 Swift暗暴的统计

主要内容:
包含很多数据.

大约10-20%的暗暴, 并部分长短暴, 高低红移和观测仪器. 暗暴的宿主星系氢柱密度明显要高一些, 说明暗暴的原因可能是dust extinction. (氢和dust有什么关系?)



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Title:		Statistical Studies of the Optically Dark Gamma-Ray Bursts in the Swift Era
Authors:		Zheng, W.; Deng, J.; Wang, J.
Publication:		eprint arXiv:0906.2244
Publication Date:		06/2009
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Extragalactic Astrophysics
Comment:		19 pages, accepted for publication in Research in Astronomy and Astrophysics (RAA)
Bibliographic Code:		2009arXiv0906.2244Z

Abstract

We compare the properties of optically dark GRBs, defined as the optical-to-X-ray spectral index beta_OX<0.5,>=4. The ratio of dark bursts is found to be about 10-20%, similar between long bursts, short ones, and the high-z sub-sample. The result for long bursts is consistent with both the pre-Swift sample and studies by other authors on smaller Swift samples. The existence of dark short GRBs is pointed out for the first time. The X-ray derived hydrogen column densities of dark GRBs clearly prefer to large values compared with those of normal bursts. This supports the dust extinction scenario as the main cause of dark GRBs. Other possibilities like very high redshift and non-standard emission mechanisms are less likely although not fully excluded.

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