TITLE: GCN CIRCULAR NUMBER: 19946 SUBJECT: GRB 160925A: MITSuME Akeno Optical Observations DATE: 16/09/27 10:33:25 GMT FROM: Taketoshi Yoshii at Tokyo Tech T.Fujiwara, T. Yoshii, Y.Saito, R.Itoh, Y. Tachibana, Y.Ono, S.Harita, T.Ozawa, K.Saisho, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We observed the field of GRB 160925A (C. Guidorzi et al., GCN Circular #19939) 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 2016-09-26 12:21:13 UT (~0.75 day after the burst) and we detected the optical counterpart in Rc and Ic band. The measured magnitudes were listed as follows. We obtained following results for the magnitudes. T0+[day] MID-UT T-EXP[sec] g' Rc Ic ------------------------------------------------------------------------------------------------------- 0.75 12:53:24 480 15.96 +/- 0.04 16.00 +/- 0.05 15.93 +/- 0.06 ------------------------------------------------------------------------------------------------------- T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used GSC2.3 catalog for flux calibration.