伽玛暴(Gamma-Ray Burst)笔记。记录有关伽玛暴的新文章,另外也包括看的老文章、自己的想法、以及跟天文相关的一些东西。 Feel free to leave me a message by comments or by email.

星期二, 二月 07, 2012

Rapoport, Sharon 2011 MgII线难题

主要内容:
说60%的暴看到了强的MgII吸收系统,比AGN的多一倍!
文中提出了微引力透镜的模型。

精彩摘抄:


文章信息:

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· arXiv e-print (arXiv:1108.5235)
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Title:
Testing the gravitational lensing explanation for the MgII problem in GRBs
Authors:
Rapoport, Sharon; Onken, Christopher A.; Schmidt, Brian P.; Wyithe, J. Stuart B.; Tucker, Brad E.; Levan, Andrew J.
Publication:
eprint arXiv:1108.5235
Publication Date:
08/2011
Origin:
ARXIV
Keywords:
Astrophysics - Cosmology and Extragalactic Astrophysics
Bibliographic Code:
2011arXiv1108.5235R

Abstract

Sixty percent of gamma-ray bursts (GRBs) reveal strong MgII absorbing systems, which is a factor of ~2 times the rate seen along lines-of-sight to quasars. The discrepancy in the covering factor is most likely to be the result of either quasars being obscured due to dust, or the consequence of many GRBs being strongly gravitationally lensed. We analyze observations of GRBs that show strong foreground MgII absorption. We Monte-Carlo the distances between foreground galaxies in the HUDF and lines of sight distributed randomly within a radius derived from the covering factor, and find that galaxies are located systematically closer to the position of the observed GRBs than expected for random lines of sight. This over-density at small impact parameters is statistically more robust than the well known excess of MgII absorbers among GRB afterglow spectra, and presents a new puzzle for MgII absorption studies. The over-density cannot be explained by obscuration in the GRB sample, but is a natural consequence of gravitational lensing. Upon examining the particular configurations of galaxies near a sample of GRBs with strong MgII absorption, we find several intriguing lensing candidates. We suggest that lensing is a viable explanation of the MgII enhancement in GRBs, and outline the future observations required to test this hypothesis conclusively.
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