TITLE: GCN CIRCULAR NUMBER: 5826 SUBJECT: GRB061121: Spectroscopic Redshift DATE: 06/11/21 16:26:12 GMT FROM: Daniel Perley at U.C. Berkeley J. S. Bloom, D. A. Perley (UC Berkeley) and H.W. Chen (Chicago) report, "Following the detection of the optical afterglow (GCN 5823, GCN 5824, GCN 5825), we obtained approximately 8 spectroscopic exposures of 120-180 seconds each, beginning at ~15:36 UT with the Keck I 10m telescope + LRIS. The afterglow is strongly detected in all exposures. Based on a preliminary wavelength solution, we identify in absorption a doublet and singlet complex which we identify as redshifted Mg I 2853 Ang, Mg II 2796, 2804 Ang at z = 1.314. We suggest this is redshift of GRB 0611121. Further analysis is ongoing." This message may be cited.