[vsnet-grb-info 8369] GRB 090904B: MOA-II Optical observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9892
SUBJECT: GRB 090904B: MOA-II Optical observation
DATE:    09/09/04 15:29:08 GMT
FROM:    Kenta Nishimoto at Nagoya U/MOA-II  <nishimo at stelab.nagoya-u.ac.jp>

K. Nishimoto, T. Sako, and D. Suzuki (STE Lab, Nagoya Univ.)
on behalf of the MOA Collaboration  report:

We searched for an optical afterglow of GRB090904B (GCN9881, V. D'Elia
et al.) starting from 07:34:56.9 UT on 2009 Sep 4 (6 hours after the
burst) with the MOA-II 1.8m telescope at Mt.John observatory in New Zealand.
In a single image of a 60 sec exposure with a wideband Red filter
(center wavelength ~ 750nm and FWHM ~ 250nm), we did not find any object
within the error circle of the Swift XRT source position (GCN 9887),
except a USNO-B1.0 catalog star, 0647-0516939, which has I mag=15.10 and
the separation of 1.8 arcsec from the center of the position.

Quick estimation of the limiting magnitude is >20.5 calibrated by using
USNO-B1.0 catalog.