ON THE SIGNIFICANCE OF THE EXCESS NUMBER OF STRONG Mg II ABSORBERS OBSERVED TOWARD GAMMA-RAY BURSTS

The number of strong (equivalent width >1 [Angstrom]) Mg II absorbers observed toward gamma-ray bursts (GRBs) has been found to be statistically larger than the number of strong absorbers toward quasi-stellar objects (QSOs). We formalize this "Mg II problem" and present a detailed expla...

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Bibliographic Details
Published in:The Astrophysical journal 2013-03, Vol.766 (1), p.1-7
Main Authors: Rapoport, Sharon, Onken, Christopher A, Wyithe, J Stuart B, Schmidt, Brian P, Thygesen, Anders O
Format: Article
Language:English
Subjects:
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
Bias
COSMIC DUST
COSMIC GAMMA BURSTS
Dust
Gamma ray bursts
GRAVITATIONAL LENSES
LINE WIDTHS
RED SHIFT
RESOLUTION
Samples
SPECTRA
Statistical analysis
Statistical methods
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Summary:The number of strong (equivalent width >1 [Angstrom]) Mg II absorbers observed toward gamma-ray bursts (GRBs) has been found to be statistically larger than the number of strong absorbers toward quasi-stellar objects (QSOs). We formalize this "Mg II problem" and present a detailed explanation of the statistical tools required to assess the significance of the discrepancy. We find that the problem exists at the 4[sigma] level for GRBs with high-resolution spectra. It has been suggested that the discrepancy can be resolved by the combination of a dust obscuration bias toward QSOs, and a strong gravitational lensing bias toward GRBs. We investigate one of the two most probable lensed GRBs that we presented in our previous work (GRB020405) and find that it is not strongly gravitationally lensed, constraining the percentage of lensed GRBs to be
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/766/1/23