TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4815 SUBJECT: GRB 060223: Keck redshift DATE: 06/02/23 08:19:49 GMT FROM: Edo Berger at Carnegie Obs E. Berger (Carnegie), S. R. Kulkarni, A. Rau (Caltech), and D. B. Fox (Penn State) report on behalf of a large collaboration: "Starting on 2006, Feb 23.2875 UT (39 min after the burst) we obtained spectroscopic observations of the optical afterglow of GRB 060223 (GCNs 4813,4814) using LRIS on the Keck-I 10-m telescope. In a single 720 sec exposure we detect a broad absorption profile which we identify as Lyman-alpha at a redshift z=4.41, as well as metal absorption features from OI, SiII, SiII*, etc at the same redshift."