GCN Circular 32014

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

We observed the field of GRB 220506A (Urabe et al. GCN Circular
#32001, Evans et al. GCN Circular #32005, Osborne et al. GCN Circular
#32006, Hu et al. GCN Circular #32008, Swain et al. GCN Circular
#32012) 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
2022-05-06 13:00:47 UT (6.5 hours after the MAXI/GSC trigger). We
stacked the images with good conditions. Additionally, we performed
the other follow-up observation starting at 2022-05-09 16:12:56 UT. We
did not detect any uncatalogued sources within the XRT error region
(Osborne et al. GCN Circular #32006). We obtained the 5-sigma limits
of the stacked images as follows.

T0+[hour] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
8.2 2022-05-06 14:42:28 240 g'>16.9, Rc>17.0, Ic>16.6
34.2 2022-05-07 16:37:41 8580 g'>18.9, Rc>19.5, Ic>18.8
82.9 2022-05-09 17:21:47 6660 g'>19.0, Rc>19.4, Ic>19.0
------------------------------------------------------------------------------------------------
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).