GCN Circular 31776

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

We observed the field of GRB 220319A (K. L. Page et al. GCN Circular
#31769, V.Lipunov et al. GCN Circular #31770, M.R. Goad et al. GCN
Circular #31771, J. D. Gropp et al. GCN Circular #31772, S. Belkin et
al. GCN Circular #31773, R. Strausbaugh et al. GCN Circular #31774, A.
de Ugarte Postigo et al. GCN Circular #31775) 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 10 sec exposures
started at 2022-03-19 17:41:30 UT (56.7 seconds after Swift BAT
trigger). We stacked the images with good conditions. We did not
detect any sources within the XRT error region (M.R. Goad et al. GCN
Circular #31771). We obtained the 5-sigma limits of the stacked images
as follows.

T0+[sec] | MID-UT | T-EXP[sec] | 5-sigma limits
-------------------------------------------------------------
101  | 2022-03-19 17:42:14 | 50   | g'>17.0, Rc>16.8, Ic>16.5
762  | 2022-03-19 17:53:16 | 560  | g'>18.5, Rc>18.3, Ic>17.9
4925 | 2022-03-19 19:02:38 | 5520 | g'>19.8, Rc>19.9, Ic>19.6
-------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time

We used 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).