[vsnet-grb-info 28066] GRB 210610A: MITSuME Ishigaki optical observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30169
SUBJECT: GRB 210610A: MITSuME Ishigaki optical observation
DATE:    21/06/10 19:54:13 GMT
FROM:    Takashi Horiuchi at Ishigakijima Astronomical Obs  <takashi.horiuchi at nao.ac.jp>

Takashi Horiuchi, Hidekazu Hanayama (NAOJ), Katsuhiro L. Murata,
Yoichi Yatsu, Nobuyuki Kawai (Tokyo Tech) 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 105 cm
Murikabushi telescope of Ishigakijima Astronomical Observatory,
Okinawa, Japan.

The observation with a series of 60 sec exposures started on
2021-06-10 15:40:04 UT (37 min after Swift BAT trigger).
We detected the point source at the position consistent with
the afterglow reported by K. L. Page et al. GCN Circular #30160.
Here, we removed bad data (images) with wrong sky conditions
and obtained the magnitudes as follows:

T0+[min] MID-UT T-EXP[sec] measured magnitudes
------------------------------------------------------------------------------------------------
37 2021-06-10T15:57:45  900 (60s × 15)  g'=19.41+/-0.14, Rc=18.19+/-0.04, Ic=17.73+/-0.10
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
The SDSS catalog (DR16) is used for flux calibration.