TITLE: GCN CIRCULAR NUMBER: 27576 SUBJECT: GRB 200412B: MITSuME Akeno optical observation DATE: 20/04/14 11:52:40 GMT FROM: Ogawa Futa at Tokyo Institute of Technology F. Ogawa, R. Adachi, R. Hosokawa, K. L. Murata, M. Niwano, N. Nakamura, Y. Yatsu, and N. Kawai(TokyoTech) report on behalf of the MITSuME collaboration: We searched for the optical counterpart of GRB 200412B (The Fermi GBM team, GCN Circular #27547) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan. The observation started on 2020-04-13 15:27:09 UT. We detected the point source at the position consistent with the afterglow detected previously (E. Gorbovskoy et al. GCN #27555). We measured the magnitudes as follows. T0+[hour] MID-UT T-EXP[sec] measured magnitudes ------------------------------------------------------------------------------------------------ 30.2 2020-04-13 17:19:02 10800 g'=20.1+/-0.2,Rc=19.6+/-0.2,Ic=19.5+/-0.2 ------------------------------------------------------------------------------------------------ T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used GSC2.3 catalog for flux calibration. The magnitudes are expressed in the Vega system.