GCN Circular 29805

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

We observed the field of GRB 210410A (The Fermi GBM team et al. GCN
Circular #29777, A. Melandri  et al. GCN Circular #29778, V. Lipunov et al.
GCN Circular #29779, M. Jelinek et al. GCN Circular #29780, M. Arimoto et
al. GCN Circular #29781, A. Ursi et al. GCN Circular #29782, Nat Butler et
al. GCN Circular #29784, Nat Butler et al. GCN Circular #29786, Paul Kuin
et al. GCN Circular #29787, J. Wood et al. GCN Circular #29788, A. D'Ai  et
al. GCN Circular #29790, A. Y. Lien et al. GCN Circular #29793, A. Ridnaia
et al. GCN Circular #29797, A. Ursi  et al. GCN Circular #29798) 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 60 sec exposures started at 2021-04-10 13:35 (9.7 hours after the
Fermi/GBM trigger). We stacked the images with good conditions. We did not
detect the optical afterglow reported previously (Jelinek et al. GCN
Circular #29780, Butler et al. GCN Circular #29784) in all three bands. We
obtained the 5-sigma limits of the stacked images as follows.

T0+[hour] MID-UT T-EXP[sec] 5-sigma limits
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10.0 14:00:15 1740 g'>19.3, Rc>19.6, Ic>19.0
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T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used the 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).