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Paper: Heavy Element Abundances and Dust Depletions in the Host Galaxies of Three Gamma-Ray Bursts
Volume: 312, Third Rome Workshop on Gamma-Ray Bursts in the Afterglow Era
Page: 271
Authors: Savaglio, S.; Fall, S.M.; Fiore, F.
Abstract: We have derive heavy element column densities in three gamma-ray burst (GRB) optical transients, associated with the circumburst or interstellar medium (ISM) of the host galaxy. In comparison with the same elements observed in damped Lyman-α (DLA) systems along QSO sight lines, we find much higher column densities of ZnII. Very small [Fe/Zn], [Si/Zn], and [Cr/Zn] values in GRB-DLAs is also indicating larger dust depletions. This appears to be in contradiction with the low reddening typically seen in GRBs. One possible way to reconcile is a dust grain-size distribution biased toward big grains, which would give a grey extinction. Our finding support the idea that primarily optically selected QSOs probe mainly the low gas/dust ISM of high redshift galaxies, while the more powerful GRBs can be detected in denser regions (molecular clouds and star forming regions).
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