TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3233
SUBJECT: GRB 050401: Optical limit
DATE:    05/04/11 11:57:48 GMT
FROM:    Ken ichi Torii at RIKEN  <torii@crab.riken.go.jp>

K. Torii (Osaka U.) reports

 "The error region of GRB 050401 (Angelini, et al. GCN 3161; Barbier,
et al. GCN 3162) was observed with the ART 14-inch telescope. BVRcIc
imaging started at 2005 April 1, 14:22:23 UT (128-s after trigger) and
60-s exposure in each filter was repeated.

 The optical afterglow (McNaught & Price GCN 3163) is not detected in
our frames and the following 3-sigma upper limits are derived relative
to USNO-B1.0 magnitudes.

MeanEpoch(UT) Magnitude Exposure
14:22:53 >12.8Rc 60s
14:24:02 >13.2Ic 60s
14:27:27 >13.4Rc 60s
14:28:34 >13.4Ic 60s
14:32:00 >13.7Rc 60s
14:33:07 >14.0Ic 60s
"