TITLE: GCN GRB OBSERVATION REPORT NUMBER: 851 SUBJECT: GRB 000926: Improved Absorber Redshift DATE: 00/10/14 23:58:55 GMT FROM: George Djorgovski at Caltech/Palomar Sandra M. Castro, S. G. Djorgovski, S. R. Kulkarni, J. S. Bloom, T. J. Galama, F. A. Harrison (Caltech), and D. A. Frail (NRAO), report on behalf of a large collaboration: We analysed high-resolution spectra of the optical afterglow of GRB 000926 kindly obtained at the WMKO Keck-II telescope by L. Cowie, A. Barger, et al. on UT 2000 September 29.26, using the ESI instrument (an Echelle spectrograph). Our preliminary analysis yields a single absorption system including the following lines: Si II 1526.7, C IV 1548.2 and 1550.5, Al II 1670.8, Si II 1808.0, Al III 1854.7 and 1862.8, Zn II 2026.1, Fe II 2344.2, 2373.7, 2382.8, 2586.6, and 2600.2, Mg II 2796.3 and 2803.5, and Mg I 2853.0. The mean redshift is z = 2.0369 +- 0.0007, presumably corresponding to the system identified by Fynbo et al. (GCN 807) as having z ~ 2.066. However, we see no evidence for any other absorption systems in these data; in particular, the ostensible system at z = 1.378 proposed by Fynbo et al. is likely due to line misidentifications. We note that the line equivalent widths appear to be unusually strong in comparison to the general population of metallic line absorbers seen in the spectra of quasars, suggesting a high column density and/or metallicity of the intervening gas. A more detailed analysis is in progress. This note can be cited.