TITLE: GCN CIRCULAR NUMBER: 23372 SUBJECT: GRB 181022A: MITSuME Akeno optical upper limits DATE: 18/10/23 15:22:37 GMT FROM: Yutaro Tachibana at Tokyo Tech K. Iida, Y. Tachibana, R. Itoh, K. L. Murata, S. Harita, K. Morita, K. Shiraishi, M. Niwano, 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 181022A (F. E. Marshall et al., GCN Circular #23364) 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 17:32:02.95 UT. We did not find any point source at the enhanced position of the XRT error circle (F. E. Marshall et al., GCN Circular #23364) in all three bands. We obtained following 3-sigma upper limits for the magnitudes. T0+[min] MID-UT T-EXP[sec] g' Rc Ic ------------------------------------------------------------------------------------------------------- 109.95 18:29:22 420 >18.4 >18.2 >17.7 ------------------------------------------------------------------------------------------------------- T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used GSC catalog for flux calibration.