GRB 210212A: MITSuME Akeno optical upper limits

We observed the field of GRB 210212A (Troja et al. GCN #29487, Beardmore et al. GCN #29489, Palmer et al. GCN #29491, Kuin et al. GCN #29492, Hu et al. GCN #29494, Tohuvavohu et al. GCN #29495) 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 with a series of 60 sec exposures started at 2021-02-12 08:51:45 UT(4.43 hours after the Swift BAT trigger). We stacked the images with good conditions. We did not find any new point sources within the enhanced Swift XRT circle (Beardmore et al. GCN #29489) in all three bands. We obtained the 5-sigma limits of the stacked images as follows. T0+[hour] MID-UT T-EXP[sec] 5-sigma limits ------------------------------------------------------------------------------------------------ 8.6 13:05:08 5400 g'>18.6, Rc>18.5, Ic>17.8 ------------------------------------------------------------------------------------------------ T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used the PS1 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. 2021, PASJ, Vol.73, Issue 1, Pages 4-24; https://github.com/MNiwano/Eclaire).