TITLE: GCN CIRCULAR NUMBER: 14465 SUBJECT: GRB 130427A: MITSuME Okayama Optical Observation DATE: 13/04/27 16:22:27 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 collaboration: We observed the field of GRB 130427A (Masell et al., GCNC 14448) 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 013-04-27 10:57:02 UT (~3.2 h after the burst). We detected the previously reported afterglow (Elenin et al., GCNC 14450) in all the three bands. Photometric results of the OT are listed below. We used SDSS catalog for flux calibration. #T0+[day] MID-UT T-EXP[sec] g' g'_err Rc Rc_err Ic Ic_err ----------------------------------------------------------------------- 0.13478 11:02:01 540.0 15.82 0.03 15.48 0.02 15.04 0.03 0.30675 15:09:39 540.0 16.45 0.06 16.27 0.03 15.87 0.04 ------------------------------------------------------------------------ T0+ : Elapsed time after the burst [day] T-EXP: Total Exposure time [sec]