[vsnet-grb-info 26767] GRB 201104B: MITSuME Akeno optical observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  28870
SUBJECT: GRB 201104B: MITSuME Akeno optical observation
DATE:    20/11/09 09:47:55 GMT
FROM:    Ryohei Hosokawa at Tokyo Institute of Technology  <hosokawa at hp.phys.titech.ac.jp>

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

We observed the field of GRB 201104B (B. Sbarufatti et al., GCN
#28825) 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
2020-11-05 08:14:33 UT. The first 29 images were heavily affected by
twilight at Akeno Observatory. We marginally detected the point source
at the position consistent with the afterglow detected previously
(Marshall et al., GCN #28827, Vielfaure et al., GCN #28840, Oates et
al., GCN #28851, Belkin et al., GCN #28852, Belkin et al., GCN #28856,
and Gupta et al., GCN #28860).

We measured the magnitudes as follows.
T0+[hour] MID-UT T-EXP[sec] measured magnitudes
------------------------------------------------------------------------------------------------
15.2 2020-11-05 12:59:59 21360 g'=21.5+/-0.3, Rc=20.7+/-0.2, Ic=20.3+/-0.3
------------------------------------------------------------------------------------------------
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.,
https://doi.org/10.1093/pasj/psaa091,
https://arxiv.org/abs/2008.11486; https://github.com/MNiwano/Eclaire).