TITLE: GCN CIRCULAR NUMBER: 18267 SUBJECT: GRB 150910A: MITSuME Okayama Optical Observation DATE: 15/09/10 11:41:03 GMT FROM: Daisuke Kuroda at OAO/NAOJ D. Kuroda, K. Yanagisawa, Y. Shimizu, H. Toda (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 150910A (Pagani et al., GCNC 18264) with the optical three color (g', Rc and Ic) CCD camera attached to the MITSuME 50cm telescope of Okayama Astrophysical Observatory. The observation started on 2015-09-10 10:20:44 UT (~1.3 h after the burst). We detected the previously reported afterglow (Pagani et al., GCNC 18264; Zheng and Filippenko, GCNC 18265; Dichiara et al., GCNC 18266) in all the three bands. Photometric results of the OT are listed below. We used SDSS-DR7 catalog for flux calibration. #T0+[day] MID-UT T-EXP[sec] g' g'_err Rc Rc_err Ic Ic_err ----------------------------------------------------------------------- 0.05630 10:25:52 540.0 17.6 0.2 18.4 0.2 17.0 0.1 ------------------------------------------------------------------------ T0+ : Elapsed time after the burst [day] T-EXP: Total Exposure time [sec]