GCN Circular 31891

K. L. Murata, M. Niwano, Y. Imai, N. Ito, Y. Takamatsu, S. Sato, R.
Hosokawa, M. Sasada, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf
of the MITSuME collaboration:

We observed the field of GRB 220412A (Klingler et al. GCN Circular #31881,
Watson et al. GCN Circular #31882, Breeveld and Klingler et al. GCN
Circular #31885, Evans et al. GCN Circular #31887, D'Ai et al. GCN Circular
#31888) with the optical three color (g', Rc, and Ic) CCD cameras attached
to the MITSuME 50 cm telescope Akeno. The observation with a series of 60
sec exposures started at 2022-04-12 10:10:00 UT (214 minutes after the
Swift/BAT trigger). We stacked the images with good conditions. We did not
detect any uncatalogued sources within the enhanced XRT error region (Evans
et al. GCN Circular #31887). We obtained the 5-sigma limits of the stacked
images as follows.

T0+[min] MID-UT T-EXP[sec] 5-sigma limits
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214 2022-04-12 10:53:37 3960 g'>19.0, Rc>19.3, Ic>18.8
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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).