TITLE: GCN CIRCULAR NUMBER: 23711 SUBJECT: GRB190109B: MITSuME Akeno optical upper limits DATE: 19/01/15 11:15:43 GMT FROM: Motoki Oeda at Tokyo Inst. of Tech. 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 (TokyoTech) report on behalf of the MITSuME collaboration: We searched for the optical counterpart of GRB 190109B (B. Sbarufatti et al.,GCN Circular #23648) 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 11:57:03.81 UT. We did not find any new point source within the enhanced XRT circle (A.P. Beardmore et al., GCN Circular #23652) in all three bands. We obtained following 5 sigma limits for the magnitudes. T0+[min] MID-UT T-EXP[sec] g' Rc Ic ------------------------------------------------------------------------------------------------------- 0.913 11:57:33.81 60 >17.54 >17.26 >16.72 0.913 12:31:59.3 3660 >19.29 >17.67 >17.12 ------------------------------------------------------------------------------------------------------- T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used UCAC-4 catalog for flux calibration.