Y. Sheffer et al 2009 ApJ 701 L63 doi:10.1088/0004-637X/701/2/L63
Y. Sheffer1, J. X. Prochaska2,3, B. T. Draine4, D. A. Perley5 and J. S. Bloom5
Show affiliationsGRB 080607 has provided the first observational signatures of molecular absorption bands toward any galaxy hosting a gamma-ray burst (GRB). Despite the identification of dozens of features as belonging to various atomic and molecular (H2 and CO) carriers, many more absorption features remained unidentified. Here, we report on a search among these features for absorption from vibrationally excited H2, a species that was predicted to be produced by the UV flash of a GRB impinging on a molecular cloud. Following a detailed comparison between our spectroscopy and static, as well as dynamic, models of H2* absorption, we conclude that a column density of 1017.5±0.2 cm–2 of H2* was produced along the line of sight toward GRB 080607. Depending on the assumed amount of dust extinction between the molecular cloud and the GRB, the model distance between the two is found to be in the range 230-940 pc. Such a range is consistent with a conservative lower limit of 100 pc estimated from the presence of Mg I in the same data. These distances show that substantial molecular material is found within hundreds of pc from GRB 080607, part of the distribution of clouds within the GRB host galaxy.
galaxies: ISM; gamma rays: bursts; ISM: clouds; ISM: molecules; molecular processes
98.70.Rz &ggr;-ray sources; &ggr;-ray bursts
95.30.Ft Molecular and chemical processes and interactions
98.38.Dq Molecular clouds, H2 clouds, dense clouds, and dark clouds
Issue 2 (2009 August 20)
Received 2009 June 13, accepted for publication 2009 July 13
Published 2009 July 30
Y. Sheffer et al 2009 ApJ 701 L63
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