1999ApJ...517..168G

If gamma-ray bursts originate in dense star-forming regions, the interstellar material can imprint detectable absorption features on the observed X-ray spectrum. Such features can be detected by existing and planned X-ray satellites, as long as the X-ray afterglow is observed within a few minutes of the burst. If the column density of the interstellar material exceeds ∼10²³ cm^–2 there exists a possibility of detecting the Kα fluorescent iron line, which should be visible for more than 1 yr, long after the X-ray afterglow continuum has faded away. Detection of these X-ray features will make possible the determination of the redshift of gamma-ray bursts even when their optical afterglow is severely dimmed by extinction.