TITLE: GCN CIRCULAR NUMBER: 24288 SUBJECT: GRB 190427A: MITSuME Akeno optical upper limits DATE: 19/04/27 15:58:22 GMT FROM: Katsuhiro L. Murata at Nagoya U K. L. Murata, M. Oeda, K.Shiraishi, K. Iida, M. Niwano, R. Adachi, Y. Yatsu, and N. Kawai (TokyoTech) report on behalf of the MITSuME collaboration: We searched for the optical counterpart of GRB 190427A (Tohuvavohu et al., GCN Circular #24261) 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 13:16:48 UT. We did not find any new point sources within the BAT circle (Tohuvavohu et al., GCN Circular #24261) in all three bands. We obtained the following 5-sigma limits for the magnitudes. T0+[hour] MID-UT T-EXP[sec] 5-sigma limits ------------------------------------------------------------------------------------------------ ~8.7 13:35:08 1620(g'),1560(Rc),1980(Ic) g'>17.8,Rc>18.2,Ic >18.6 ------------------------------------------------------------------------------------------------ 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 AB system.