[vsnet-grb-info 7712] GRB 090426: Okayama MITSuME optical observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9266
SUBJECT: GRB 090426: Okayama MITSuME optical observation
DATE:    09/04/26 23:13:33 GMT
FROM:    Michitoshi Yoshida at Okayama Astrophysical Obs  <yoshida at oao.nao.ac.jp>

M. Yoshida, D. Kuroda, K. Yanagisawa, Y. Shimizu, S. Nagayama,
H. Toda (OAO, NAOJ) and N. Kawai (Tokyo Tech) report on behalf
of the MITSuME collaboration:

We detected the optical afterglow of GRB 090426 (Cummings et al.
GCN 9254; Xin et al. GCN 9255; Oates et al. GCN 9265) with the
optical three color (g', Rc and Ic) CCD camera attached to the
MITSuME 50cm telescope of Okayama Astrophysical Observatory.
The observation started on 2009-04-26 12:49:50 UT (63 sec after
the alert). We found the afterglow at the UVOT position of the
GRB (Oates et al. GCN 9265) in all the three bands. It rapidly
faded from 1 min to 2 hours from the burst.

Photometric results listed below. We used GSC2.3 catalog for
flux calibration. We did not apply Galactic extinction to the
following results.

#PDAY      MID-UT   T-EXP    g'  g'_err  Rc   Rc_err  Ic   Ic_err
-----------------------------------------------------------------
0.00108  12:50:20    60.0  17.21  0.15  16.54  0.09  15.95  0.11
0.00436  12:55:04   540.0  17.81  0.08  17.30  0.08  16.90  0.10
0.01198  13:06:03   540.0  19.43  0.31  19.16  0.27  18.30  0.26
0.01116  13:04:52  1500.0  18.58  0.12  18.04  0.09  17.61  0.11
0.06343  14:20:08  3000.0  20.42  0.38  19.86  0.22  19.46  0.35
-----------------------------------------------------------------