TITLE: GCN CIRCULAR NUMBER: 18817 SUBJECT: GRB 160104A: MITSuME Akeno Optical Observation DATE: 16/01/04 12:28:39 GMT FROM: Taketoshi Yoshii at Tokyo Tech Y.Saito, T.Fujiwara, T. Yoshii, Y. Tano, Y. Tachibana, Y.Ono, S.Harita, Y.Muraki, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We searched for the optical counterpart of GRB 160104A (A. Melandri et al., GCN Circular #18815) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan. The observation started on 2016-01-04 11:24:56 UT (46 sec after the burst) and we detected the optical counterpart in Rc and Ic band. The measured magnitudes were listed as follows. We obtained following limits for the magnitudes. T0+[sec] MID-UT T-EXP[sec] g' Rc Ic ------------------------------------------------------------------------------------------------------- 61 11:25:11 30 > 18.5 17.9 +/- 0.3 16.5 +/- 0.2 ------------------------------------------------------------------------------------------------------- T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used GSC2.3 catalog for flux calibration.