[vsnet-grb-info 20885] GRB 180720B: MITSuME Akeno optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22983
SUBJECT: GRB 180720B: MITSuME Akeno optical observations
DATE:    18/07/21 02:16:27 GMT
FROM:    Ryosuke Itoh at Tokyo Institute of Tech.  <itoh at hp.phys.titech.ac.jp>

R. Itoh, K. L. Murata, Y. Tachibana, S. Harita, K. Morita,
K. Shiraishi, K. Iida, M. Oeda, R. Adachi, S. Niwano,
Y. Yatsu, and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:

We observed the optical counterpart of GRB 180720B
(Siegel et al., GCN 22973)
with the optical three color (g', Rc, and Ic) CCD cameras attached to
the MITSuME 50cm telescope of Akeno Observatory, Yamanashi, Japan.

The observation started on 2018-07-20 18:08:46 UT, (~3.8 hours after
the burst). We detected the previously reported afterglow
(Martone et al., GCN 22976, Sasada et al., GCN 22977, Reva et al., GCN 22979)
in the g', Rc and Ic band.

The photometric results of the OT are listed below.
We used UCAC-4 catalog for flux calibration.

#T0+[hour]  MID-UT    T-EXP[sec] g'   Rc   Ic
-------------------------------------------------------------------
3.8    18:14:30   540  16.53+/-0.06  16.67+/-0.06 16.25+/- 0.08
-------------------------------------------------------------------
T0+ : Elapsed time after the burst [hour]
T-EXP: Total Exposure time [sec]