GRB 191031D: MITSuME Akeno optical upper limits

We searched for the optical counterpart of GRB 191031D (The Fermi GBM team, GCN Circular #26111, V. D'Elia et al., GCN Circular #26112, Bagrat Mailyan, #26114) 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 19/11/01 08:18:36 UT. We did not find any new point sources within the XRT circle (J.P. Osborne et al., GCN Circular #26117) in all three bands. We obtained the following 5-sigma limits for the magnitudes. T0+[hour] MID-UT T-EXP[sec] 5-sigma limits ------------------------------------------------------------------------------------------------ ~11.5 09:12:34 1680 g'>18.3, Rc>18.2, Ic>17.3 ------------------------------------------------------------------------------------------------ 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.