[vsnet-grb-info 5338] GRB 071020: MITSuME Akeno optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7026
SUBJECT: GRB 071020: MITSuME Akeno optical observations
DATE:    07/10/31 11:38:14 GMT
FROM:    Nobuyuki Kawai at Tokyo Tech  <nkawai at hp.phys.titech.ac.jp>

T. Ishimura, Y. Yatsu, T. Shimokawabe, N. Kawai (Tokyo Tech) and
M. Yoshida (NAOJ) report on behalf of the MITSuME collaboration:

We observed the field of GRB 071020 (Holland et al. , GCN6949) with
the 3-color 50cm MITSuME Telescope at Akeno, Japan from UT 16:21 to
UT 19:53 on Oct. 20, 9.3 hours after the trigger.

In the co-added images of Ic and Rc bands, we detected the optical
afterglow reported by Schaefer et al. (GCN 6948).  Photometric
calibration was done using the USNO-B1.0 (Ic-band) and NOMAD (g'- and
Rc-bands) catalogs.  The results are following:

Filter  start     end         Exposure      Mag
------------------------------------------------------
g'     16:21:13  19:53:55    149 x 60s  >21.1  (3 sigma upper limit)
Rc     16:21:13  19:53:55    149 x 60s  21.2 +/- 0.3
Ic     16:21:13  19:53:55    149 x 60s  19.8 +/- 0.3
------------------------------------------------------