GRB 220117B: MITSuME Akeno optical upper limits

We observed the field of GRB 220117B (A. Melandri et al. GCN Circular #31468, V. Lipunov et al. GCN Circular #31469) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope Akeno. The observation started at 2022-01-17 20:06:58 UT (1.5 minutes after Swift trigger). We stacked the images with good conditions. We did not detect any sources within the XRT error region (A. Melandri et al. GCN Circular #31468). We obtained the 5-sigma limits of the stacked images as follows. T0+[minutes] MID-UT T-EXP[sec] 5-sigma limits ------------------------------------------------------------------------------------------------ 2.9 2022-01-17 20:08:19 80 g'>16.3, Rc>16.4, Ic>15.8 28.7 2022-01-17 20:34:10 2280 g'>16.5, Rc>17.0, Ic>16.5 ------------------------------------------------------------------------------------------------ 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).