[vsnet-grb-info 28117] GRB 210610B: MITSuME Akeno optical observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30220
SUBJECT: GRB 210610B: MITSuME Akeno optical observation
DATE:    21/06/12 06:19:18 GMT
FROM:    Ryohei Hosokawa at Tokyo Institute of Technology  <hosokawa at hp.phys.titech.ac.jp>

R. Noto, R. Hosokawa, K. L. Murata, M. Niwano, N. Ito, H. Takamatsu,
Y. Imai, 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 210610B (Page et al. GCN #30170, Ursi et
al. GCN #30195, Frederiks et al. GCN #30196, Malacaria et al. GCN
#30199) 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 2021-06-11 10:33:20 UT (14.7
hours after Swift BAT trigger). We stacked the images with good
conditions. We detected the afterglow reported previously (Page et al.
GCN #30170, Kumar et al. GCN #30174, Rumyantsev et al. GCN #30175,
Lipunov et al. GCN #30176, Hu et al. GCN #30177, Rumyantsev et al. GCN
#30178, Wet et al. GCN #30180, Romanov et al. GCN #30181, Fynbo et al.
GCN #30182, Moskvitin et al. GCN #30187, Becerra et al. GCN #30190,
Mong et al. GCN #30193, Postigo et al. GCN #30194, Marchini et al. GCN
#30198, Dutta et al. GCN #30201, Zheng et al. GCN #30204, Vreeswijk et
al. GCN #30205, Perley et al. GCN #30206, Pankov et al. GCN #30212,
Pankov et al. GCN #30215, Perley et al. GCN #30216, Laskar et al. GCN
#30217, Alexander et al. GCN #30218)

We measured the magnitudes as follows.
MID-UT T-EXP[sec] measured magnitudes
------------------------------------------------------------------------------------------------
2021-06-11 12:51:05 9780 g'=19.3+/-0.2, Rc=18.9+/-0.1, Ic=18.8+/-0.1
------------------------------------------------------------------------------------------------
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).