TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3833 SUBJECT: GRB 050820: High Resolution Spectroscopy from Keck DATE: 05/08/20 09:51:16 GMT FROM: Jason Prochaska at UCO/Lick Obs J. X. Prochaska (UCO/Lick), J. S. Bloom, J. T. Wright (UC Berkeley), R. Paul Butler (DTM, Carnegie), H. W. Chen (MIT), S.S. Vogt (UCO/Lick), and G.W. Marcy (UC Berkeley) report: "Starting at 07h28m59s 20 Aug 2005 UTC, we began spectroscopic observations of the optical transient (Fox & Cenko GCN #3829) of GRB 050820 (Page et al. GCN #3830) with HIRES/Keck I. In a series of 900 sec exposures the continuum from the afterglow is well detected as are many absorption lines. Based on the identification of a damped Ly alpha feature, SiII 1304, OI 1302, and numerous fine structure lines we measure the GRB redshift to be z=2.612 +/- 0.002." We are grateful to Derek Fox for his assistance in helping us acquire this data. This message may be cited. ---------------------------------------------- Jason X. Prochaska UCO/Lick Observatory UC Santa Cruz Santa Cruz, CA 95064 xavier@ucolick.org http://www.ucolick.org/~xavier/ 831-459-2135 (Direct) 831-459-2991 (UCO/Lick Main) 831-459-5244 (Fax)