TITLE: GCN CIRCULAR NUMBER: 14454 SUBJECT: GRB 130427A: MITSuME Akeno Optical observation(T0+8000s~) DATE: 13/04/27 11:19:18 GMT FROM: Yoichi Yatsu at Tokyo Tech. Y. Yatsu, Y. Yano, R. Usui, Y. Tachibana, K. Ito, T. Yoshii, S. Kurita, Y. Saito, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We observed GRB 130427A (Maselli et al., GCNC 14448) with an optical tri-color (g, Rc, and Ic) camera attached to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan. The observation started on 2013-04-27 10:06:09.60 UT (8293 sec after the trigger). And we found the optical counterpart reported in the twilight sky. The measured magnitudes were listed below. MID-MJD T-EXP[sec] g' Rc Ic ------------------------------------------------------------------------------------------- 56409.4231929 360 15.66+/-0.10 15.03+/-0.07 14.71+/-0.09 ------------------------------------------------------------------------------------------- T-EXP: Total Exposure time [sec] (The photon flux were calibrated against GSC2.3 catalog.)