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 <ogawa@hp.phys.titech.ac.jp> 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)