TITLE: GCN CIRCULAR NUMBER: 28684 SUBJECT: GRB 201017A: MITSuME Akeno optical upper limits DATE: 20/10/19 14:13:28 GMT FROM: Ryohei Hosokawa at Tokyo Institute of Technology R. Hosokawa, K. L. Murata, R. Adachi, M. Niwano, F. Ogawa, N. Nakamura, N. Ito, S. Ogata, H. Takamatsu, H. Hara, Y. Yatsu, and N. Kawai (TokyoTech) report on behalf of the MITSuME collaboration: We observed the field of GRB 201017A (The Fermi GBM team, GCN #28665, A. D'Ai et al., GCN #28666, V. Lipunov et al., GCN #28667, L. P. Xin et al., GCN #28672, S. Belkin et al., GCN #28679) 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 at 2020-10-17 12:53:15 UT.(186 min after trigger) Since some images were heavily affected by bad weather, we stacked the images with good conditions. We did not find any new point sources within the enhanced Swift/XRT circle (M. R. Goad et al., GCN #28671) in all three bands. We obtained the 5-sigma limits as follows T0+[min] MID-UT T-EXP[sec] 5-sigma limits ------------------------------------------------------------------------------------------------ 296 17:53:37 9480 g'>20.0,Rc>19.9,Ic>19.2 ------------------------------------------------------------------------------------------------ T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used the PS1 catalog for flux calibration. The magnitudes are expressed in the AB system. The images were processed in real-time through the MITSuME GPU reduction pipeline (Niwano et al., accepted for publication in PASJ, https://arxiv.org/abs/2008.11486; https://github.com/MNiwano/Eclaire).