TITLE: GCN CIRCULAR NUMBER: 23211 SUBJECT: GRB 180905A: MITSuME Akeno optical upper limits DATE: 18/09/06 05:53:52 GMT FROM: Katsuhiro L. Murata at Nagoya U M. Niwano, R. Itoh, K. L. Murata, Y. Tachibana, S. Harita, K. Morita, K. Shiraishi, K. Iida, R. Adachi, M. Oeda, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We searched for the optical counterpart of GRB 180905A (V. D'Elia et al., GCN Circular #23201) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50cm telescope of Akeno Observatory, Yamanashi, Japan. The observation started on 2018-09-05 17:29:51.08 UT. We did not find any point source at the enhanced position of the XRT error circle (A.P. Beardmore et al., GCN Circular #23207) in all three bands. We obtained following 5-sigma upper limits for the magnitudes. T0+[min] MID-UT T-EXP[sec] g' Rc Ic ------------------------------------------------------------------------------------------------------- 202.32 18:46:39 8,100 >18.9 >18.6 >18.4 ------------------------------------------------------------------------------------------------------- T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used UCAC-4 catalog for flux calibration.