GCN Circular 31488

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

We observed the field of GRB 220117A (A. Melandri et al. GCN Circular
#31466, S.Y. Fu et al. GCN Circular #31467, V. Lipunov et al. GCN
Circular #31470, A.P. Beardmore et al. GCN Circular #31472, J.A.
Kennea et al. GCN Circular #31477, J. Palmerio et al. GCN Circular
#31480, R. Strausbaugh et al. GCN Circular #31481, A. A. Breeveld et
al. GCN Circular #31482, D. M. Palmer et al. GCN Circular #31485, P.
Veres et al. GCN Circular #31487) 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
2022-01-18 10:26:37 UT (18.1 hours after Swift trigger). We stacked
the images with good conditions. We did not detect any sources within
the XRT error region (A.P. Beardmore et al. GCN Circular #31472). We
obtained the 5-sigma limits of the stacked images as follows.

T0+[hours] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
21.3 2022-01-18 13:34:36 7740 g'>19.0, Rc>19.5, Ic>19.2
------------------------------------------------------------------------------------------------
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).