The Interstellar Medium of GRB Host Galaxies I. Echelle Spectra of Swift GRB Afterglows

摘要

We present optical echelle spectra of four gamma-ray burst (GRB) afterglows(GRB 050730, GRB 050820, GRB 051111, and GRB 060418) discovered during thefirst 1.5 years of operation of the Swift satellite and localized by either theSwift telescope or follow-up ground-based imaging. We analyze the spectra toderive accurate column density measurements for the transitions arising in theinterstellar medium (ISM) of the GRB host galaxies. These measurements can beused to constrain the physical properties of the ISM including the metallicity,dust-to-gas ratio, ionization state, and chemical abundances of the gas. Wealso present measurements of the strong MgII systems in the GRB afterglowspectra. With the publication of this paper, we provide the first data releaseof echelle afterglow spectra by the GRAASP collaboration to the generalcommunity.