TITLE: GCN CIRCULAR NUMBER: 23408 SUBJECT: GRB 181103A: MITSuME Okayama optical upper limits DATE: 18/11/05 04:35:48 GMT FROM: Katsuhiro L. Murata at Nagoya U K. L. Murata, R. Itoh, Y. Tachibana, S. Harita, K. Morita, K. Shiraishi, K. Iida, M. Oeda, 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 181103A (A. Tohuvavohu et al., GCN Circular #23402) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of Okayama Astrophysical Observatory, Japan. The observation started on 19:38:58 UT. We did not find any new point source within enhanced XRT circle (P.A. Evans et al., GCN Circular #23403) in all three bands. We obtained following limits for the magnitudes. T0+[hour] MID-UT T-EXP[sec] g' Rc Ic ------------------------------------------------------------------------------------------------------- 15.352 20:15:29 3240 >18.5 >18.0 >17.5 ------------------------------------------------------------------------------------------------------- T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used GSC2.3 catalog for flux calibration.