TITLE: GCN CIRCULAR NUMBER: 20070 SUBJECT: GRB 161017A: MITSuME Akeno Optical Observation DATE: 16/10/18 07:08:21 GMT FROM: Taketoshi Yoshii at Tokyo Tech T.Fujiwara, Y.Saito, Y. Tachibana, T. Yoshii, Y. Yano, Y.Ono, S.Harita, Y.Muraki, K.Morita, T.Ozawa, K.Saisho,Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We searched for the optical counterpart of GRB 161017A (E. Troja et al., GCN Circular #20064) 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 2016-10-17 17:52:42 UT (51 sec after the burst) and we detected the optical counterpart in g', Rc and Ic band. The measured magnitudes were listed as follows. We obtained following results for the magnitudes. T0+[sec] MID-UT T-EXP[sec] g' Rc Ic ------------------------------------------------------------------------------------------------------- 51 17:52:57 30 14.55 +/- 0.06 13.78 +/- 0.05 13.38 +/- 0.06 87 17:55:41 240 14.35 +/- 0.05 13.61 +/- 0.04 13.25 +/- 0.04 331 18:03:41 600 15.50 +/- 0.05 14.73 +/- 0.04 14.42 +/- 0.04 996 18:28:35 2100 16.58 +/- 0.05 15.89 +/- 0.05 15.63 +/- 0.04 3320 19:15:35 2040 16.76 +/- 0.06 16.03 +/- 0.05 15.77 +/- 0.05 ------------------------------------------------------------------------------------------------------- T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used GSC2.3 catalog for flux calibration.