TITLE: GCN CIRCULAR NUMBER: 28548 SUBJECT: GRB 201001A: MITSuME Akeno optical upper limits DATE: 20/10/02 09:42:14 GMT FROM: Ryohei Hosokawa at Tokyo Institute of Technology R. Hosokawa, S. Ogata, K. L. Murata, R. Adachi, M. Niwano, F. Ogawa, N. Nakamura, N. Ito, H. Takamatsu, H. Hara, Y. Yatsu, and N. Kawai (TokyoTech) report on behalf of the MITSuME collaboration: We observed the field of GRB 201001A(Fermi GBM Team, GCN 28538; David et al., GCN 28539) 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 with a series of 60 sec exposures started at 2020-10-01 16:44:38UT. Since some images were heavily affected by the moon, we stacked the images with good conditions. We did not find any new point sources within the enhanced Swift/XRT error circle (Evans et al., GCN 28540) in the 60 sec exposure images and the stacked images. We obtained the 5-sigma limits of the stacked images as follows. T0+[hour] MID-UT T-EXP[sec] 5-sigma limits ------------------------------------------------------------------------------------------------ 6.8 2020-10-01T19:06:10.46 4020 g'>19.0, Rc>19.3, Ic>18.9 ------------------------------------------------------------------------------------------------ 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). -- ____________ 東京工業大学 河合研究室 修士1年 細川稜平 hosokawa@hp.phys.titech.ac.jp