TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3971 SUBJECT: GRB 050908: DEIMOS spectrum and further analysis DATE: 05/09/12 17:39:33 GMT FROM: Jason Prochaska at UCO/Lick Obs J. X. Prochaska (UCO-Lick/UCSC), R. J. Foley (UCB), H.-W. Chen (U Chichago), J. S. Bloom (UCB), K. Hurley (SSL/UCB), M. Cooper (UCB), R. Guhathakurta (UCO-Lick/UCSC), W. Li (UCB) report on behalf of the GRAASP collaboration: "We have obtained Keck/DEIMOS spectra of the afterglow of 050908 starting at 20050908.56 UT. The 1200/7500 grating data has a resolution of ~0.33 Ang and S/N~10 per resolution element covering wavelengths 6300-9000 Ang. We refine the GRB host redshift to be z=3.3440 +/- 0.0001 based on the strongest component of the CIV profile. The DEIMOS spectrum overlaps with GMOS spectrum between 6330 and 7950 A, and does not confirm the emission feature originally detected in the GMOS data at 7273 A. We therefore conclude that the intervening system at z=2.81 reported in GCN 3949 is not likely to be real. Adopting log N(HI)=19 and ignoring ionization corrections, the non-detections of CII 1334, OI 1302 and AlII 1670 imply a metallicity of less than 1/100 solar. Ionization corrections could imply even 10x lower values. In contrast to the low-ion transitions, the host shows very strong SiIV and CIV absorption spanning ~500 km/s." This message may be cited.