Keck Spectroscopy and HST Imaging of GRB 000926: Probing a Host Galaxy at z = 2. 038

S. Castro, T. J. Galama, F. A. Harrison, J. A. Holtzman, J. S. Bloom, S. G. Djorgovski, S. R. Kulkarni

Published 2001-10-25Version 1

We present early-time Keck spectroscopic observations and late-time Hubble Space Telescope (HST) imaging of GRB 000926. The HST images show a small offset between the optical transient and the compact host galaxy. Combined with the large equivalent widths measured for metallic absorption lines by the Keck Echellette Spectrograph and Imager (ESI) and the Low-Resolution Imaging Spectrometer (LRIS), this indicates that the GRB exploded near the center of its host. The ESI spectroscopy reveals two absorption systems centered at z = 2.0379 \pm 0.0008 with a velocity separation of 168 km s^{-1}, which we interpret as being due to individual clouds in the host galaxy. The ratios of chromium to zinc equivalent widths indicates the host is depleted in dust relative to local values to a similar degree as damped Lyman alpha systems at the same redshift. Further, the two clouds appear to have similar relative metal abundance and dust to gas ratio. If one cloud is associated with the GRB site, this implies the explosion did not significantly alter the surrounding environment.