TITLE: GCN CIRCULAR NUMBER: 11306 SUBJECT: GRB100925A/MAXI J1659-152 MITSuME Ishigakijima and Okayama Optical Observation DATE: 10/09/26 08:20:38 GMT FROM: Daisuke Kuroda at OAO/NAOJ D. Kuroda (OAO, NAOJ), H. Hanayama (IAO, NAOJ), K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ), S. Nagayama, T. Miyaji, J. Watanabe (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto) and N. Kawai(Tokyo Tech) report on behalf of the MITSuME collaboration: We observed the field of GRB 100925A / MAXI J1659-152 (Mangano et al., GCN 11296; Barthelmy et al., GCN 11300) with the optical three color (g', Rc and Ic) CCD camera attached to the MITSuME 50cm telescope of Okayama Astrophysical Observatory and the Murikabushi 1m telescope of Ishigakijima Astronomical Observatory. We detected the previously reported source at the UVOT position (Marshall, GCN 11298) in all the three bands. Photometric results of the OT are listed below. We used GSC2.3 catalog for flux calibration. Okayama Astrophysical Observatory: The observation started on 2010-09-25 09:58:43 UT (~ 1.9 h after the trigger). #T0+[day] MID-UT T-EXP[sec] g' g'_err Rc Rc_err Ic Ic_err ---------------------------------------------------------------------- 0.08949 10:13:57 1560.0 17.13 0.06 16.46 0.03 16.45 0.16 0.11081 10:44:39 1500.0 17.08 0.08 16.61 0.04 16.32 0.19 0.13201 11:15:11 1560.0 17.15 0.09 16.46 0.05 15.98 0.15 Ishigakijima Astronomical Observatory: The observation started on 2010-09-25 10:53:50 UT (~ 2.8 h after the trigger). #T0+[day] MID-UT T-EXP[sec] g' g'_err Rc Rc_err Ic Ic_err ---------------------------------------------------------------------- 0.12082 10:59:03 480.0 16.97 0.04 16.48 0.02 16.24 0.03 0.12818 11:09:40 540.0 17.05 0.03 16.52 0.02 16.32 0.03 0.13556 11:20:17 540.0 17.02 0.04 16.52 0.02 16.30 0.02 T0+ : Elapsed time after the burst [day] T-EXP: Total Exposure time [sec]