TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5513 SUBJECT: GRB 060904B: VLT redshift DATE: 06/09/04 09:33:08 GMT FROM: Daniele Malesani at SISSA-ISAS,Trieste,Italy D. Fugazza, P. D'Avanzo (INAF/OABr), D. Malesani (SISSA), G. Tagliaferri (INAF/OABr), G. Chincarini (Univ. Milano-Bicocca), L. Stella (INAF-OAR), J.P.U. Fynbo (DARK/NBI), C. Lidman, H. Sana (ESO), report on behalf of the MISTICI collaboration. We observed the optical counterpart of GRB 060904B (Grupe et al., GCN 5505; Rykoff et al., GCN 5504). Spectroscopy was performed with VLT + FORS1, with mean time Sep 4.318 UT (5.15 hr after the burst). Several absorption features were clearly identified, among which FeII 2586, FeII 2600, Mg II 2795,2803, Mg I 2852, Ca H&K 3933,3968. The inferred redshift is z = 0.703. We acknowledge excellent support from the ESO staff. This message can be cited.