TITLE: GCN CIRCULAR NUMBER: 23590 SUBJECT: GRB 181228A: MITSuME Akeno optical upper limits DATE: 18/12/30 12:22:33 GMT FROM: Katsuhiro L. Murata at Nagoya U M. Oeda, K. L. Murata, R. Itoh, Y. Tachibana, S. Harita, K. Morita, K. Shiraishi, K. Iida, M. Niwano, R. Adachi, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We searched for the optical counterpart of GRB 181228A (M. J. Moss et al., GCN Circular #23570) 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 09:04:35.19 UT. We did not find any new point source within the enhanced XRT circle (A.P. Beardmore et al., GCN Circular #23574) in all three bands. We obtained following limits for the magnitudes. T0+[hour] MID-UT T-EXP[sec] g' Rc Ic ------------------------------------------------------------------------------------------------------- 6.188 13:04:51 25320 >19.1 >19.0 >18.6 ------------------------------------------------------------------------------------------------------- T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used UCAC-4 catalog for flux calibration.