TITLE: GCN CIRCULAR NUMBER: 26776 SUBJECT: GRB 200115A: MITSuME Okayama optical upper limits DATE: 20/01/15 15:01:10 GMT FROM: Masafumi Niwano at Tokyo Institute of Tech M. Niwano, K. L. Murata, M. Oeda, K. Shiraishi, K. Iida, R. Adachi, F. Ogawa, S. Toma, R. Hosokawa, N. Nakamura, Y. Yatsu, and N. Kawai(TokyoTech) report on behalf of the MITSuME collaboration: We searched for the optical counterpart of GRB 200115A (S. B. Cenko et al.,GCN Circular #26771) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of Okayama Astrophysical Observatory, Okayama, Japan. The observation started on 11:52:38.68 UT. We did not find any new point sources within the Swift/BAT circle (S. B. Cenko et al., GCN Circular #26771) in all three bands. We obtained the 5-sigma limits as follows. T0+[sec]   MID-UT    T-EXP[sec]    5-sigma limits ------------------------------------------------------------------------------------------------ 135   12:23:04.98   3060   g'>18.3, Rc>17.6, Ic>17.2 ------------------------------------------------------------------------------------------------ T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used UCAC4 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. ,in prep; https://github.com/MNiwano/Eclair)