TITLE: GCN CIRCULAR NUMBER: 18758 SUBJECT: GRB 151228B: MITSuME Akeno optical upper limits DATE: 15/12/29 21:44:48 GMT FROM: Taketoshi Yoshii at Tokyo Tech Y.Muraki, T.Fujiwara, T. Yoshii, Y. Saito, Y. Tachibana, Y.Yano, S.Harita, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We searched for the optical counterpart of GRB 151228B (A. Y. Lien et al., GCN Circular #18739) 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 2015-12-29 09:55:19 UT (~11.1 h after the burst). We did not find any new point source within Swift/XRT circle in all three bands. We obtained following limits for the magnitudes. T0+[sec] MID-UT T-EXP[sec] g' Rc Ic ------------------------------------------------------------- 40085 10:37:06 2507 > 20.9 > 20.6 > 19.6 ------------------------------------------------------------- T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used GSC2.3 catalog for flux calibration.