GCN Circular 12777
A. Cucchiara (UCSC/UCO Lick), A. J. Levan (U. Warwick), and N. Tanvir (U. Leicester) report: On December 30.05 UT (157 minutes after the BAT trigger) we observed the field of GRB 111229A (Lien et al., GCN 12774) using GMOS-South on the Gemini-South 8-m telescope. An optical afterglow is detected at a position reported by Nicuesa Guelbenzu et al. (GCN 12775). Subsequent spectroscopic observation of the optical afterglow of GRB 111229A (range 5900-10080 Angstroms) reveals several absorption features, including FeII2586,2600, MnII2606, MgII2796,2803 and MgII2853 at a common redshift of 1.3805. We therefore suggest this to be the redshift of GRB 111229A. We thank the Gemini staff for performing this observation, in particular Pascale Hibon.