TITLE: GCN CIRCULAR NUMBER: 22001 SUBJECT: GRB 171010A: MITSuME Akeno Optical Observation DATE: 17/10/12 02:53:40 GMT FROM: Katsuhiro L. Murata at Nagoya U S. Harita, R. Itoh, K. L. Muarata, Y. Tachibana, T. Yoshii, K. Morita, T. Ozawa, H. Mamiya, K. Shiraishi, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We have been observing the optical counterpart of GRB 171010A (N. Omodei et al., GCN Circular #21985) 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 2017-10-11 13:29:52.24 UT. We detected the previously reported optical afterglow (Thorstensen & Halpern, GCN Circular #21987; Izzo & Malesani, GCN Circular #21988; Guidorzi et al., GCN Circular #21991; Malesani et al., GCN Circular #22000) in Ic and Rc bands. The measured magnitudes were listed as follows. T0+[hour] MID-UT T-EXP[sec] g' Rc Ic ------------------------------------------------------------------------------------------------------- ~18.29 15:23:32 4380 >18.8 18.04+/- 0.16 17.331 +/- 0.12 ------------------------------------------------------------------------------------------------------- T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used GSC2.3 catalog for flux calibration.