TITLE: GCN CIRCULAR NUMBER: 19599 SUBJECT: GRB 160625B: MITSuME Ishigakijima Optical Observation DATE: 16/06/27 02:51:23 GMT FROM: Daisuke Kuroda at OAO/NAOJ D. Kuroda (OAO, NAOJ), H. Hanayama, T. Miyaji, J. Watanabe (IAO, NAOJ), K. Yanagisawa (OAO, NAOJ), S.Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto) and N. Kawai(Tokyo Tech) report on behalf of the MITSuME and OISTER collaboration: We observed the field of GRB 160625B (Dirirsa et al., GCNC 19580; Melandri et al., GCNC 19585) with the optical three color (g', Rc and Ic) CCD camera attached to the Murikabushi 1m telescope of Ishigakijima Astronomical Observatory. The observation started on 2016-06-26 14:03:44 UT (~15.3 h after the burst). We detected the previously reported afterglow (Troja et al., GCNC 19588) in in all the three bands. The photometric results of the OT are listed below. We used GSC2.3 catalog for flux calibration. #T0+[day] MID-UT T-EXP[sec] g' g'_e Rc Rc_e Ic Ic_e ------------------------------------------------------------------- 0.64273 14:08:57 540.0 19.16 0.10 18.59 0.05 18.08 0.10 0.73075 16:15:41 540.0 19.27 0.08 18.78 0.06 18.28 0.08 ------------------------------------------------------------------- T0+ : Elapsed time after the burst [day] T-EXP: Total Exposure time [sec]