GCN Circular 30596

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

We observed the field of GRB 210802A (V. Lipunov et al. GCN Circular
#30586, P. A. Evans et al. GCN Circular #30587, F. Longo et al. GCN
Circular #30589, O.J. Roberts et al. GCN Circular #30590, B.
Sbarufatti et al. GCN Circular #30591, Y.-D. Hu et al. GCN Circular
#30592, Alan M. Watson et al. GCN Circular #30593) with the optical
three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm
telescope Okayama. The observation with a series of 60 sec exposures
started at 2021-08-03 10:34:24 UT (14.4 hours after Fermi trigger). We
stacked the images with good conditions. We did not detect any
uncatalogued sources within the XRT error region (B. Sbarufatti et al.
GCN Circular #30591). We obtained the 5-sigma limits of the stacked
images as follows.

T0+[hour] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
15.8 2021-08-03 11:54:24 1080 Rc>17.2, Ic>16.9
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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).