TITLE: GCN CIRCULAR NUMBER: 27813 SUBJECT: GRB 200524A: MITSuME Akeno optical observation DATE: 20/05/25 07:18:07 GMT FROM: Ogawa Futa at Tokyo Institute of Technology F. Ogawa, R. Hosokawa, R. Adachi, K. L. Murata, M. Niwano, N. Nakamura, Y. Yatsu, and N. Kawai (TokyoTech) report on behalf of the MITSuME collaboration: We observed the field of GRB 200524A (Fermi-LAT detection: Dirirsa et al., GCN #27797, Fermi-GBM detection: Pookalil et al., GCN #27809, Swift-XRT afterglow detection: Capalbi et al. GCN #27811, and others) 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 13:07:01.89 UT. We detected a point source clearly in g' and Rc band, and marginally in Ic band at the position consistent with the afterglow reported previously (Ho et al., GCN #27799, Kumar et al., GCN #27800, Rumyantsev et al., GCN #27802, Sanwal et al., GCN #27803, Perley et al., GCN #27805, Kumar et al., GCN #27806, de Ugarte Postigo et al., GCN #27807, Blazek et al., GCN #27810). We measured the magnitudes as follows. T0+[hour] MID-UT T-EXP[sec] measured magnitudes ------------------------------------------------------------------------------------------------ 8.03 13:10:54 420 g'=19.6+/-0.3, Rc=19.5+/-0.3, Ic=19.4+/-0.5 ------------------------------------------------------------------------------------------------ T0+: Elapsed time after the burst T-EXP: Total Exposure time We used GSC2.3 catalog for flux calibration. The magnitudes are expressed in the Vega system. The images were processed in real-time through the MITSuME GPU reduction pipeline (Niwano et al. ,in prep; https://github.com/MNiwano/Eclair)