GCN Circular 30161

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

We observed the field of GRB 210610A (K. L. Page et al. GCN
Circular #30160) with the optical three color (g', Rc, and Ic) CCD
cameras attached to the
MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan. The
observation with a series of 10 sec exposures started at 2021-06-10
15:04:41 UT (58 seconds after Swift BAT trigger). We stacked the
images with good conditions. We detected the point source at the
position consistent with the afterglow detected previously (K. L. Page
et al. GCN Circular #30160)
We measured the magnitudes as follows.

filter MID-UT T-EXP[sec] measured magnitudes
------------------------------------------------------------------------------------------------
g' 15:08:47 10 16.4+/-0.4
Rc 15:08:29 50 15.3+/-0.1
Ic 15:08:29 50 15.0+/-0.2
------------------------------------------------------------------------------------------------
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).