TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  5541
SUBJECT: GRB060904b optical detections (delayed report due to internet outage)
DATE:    06/09/07 02:58:40 GMT
FROM:    Gottfried Kanbach at MPE  <gok@mpe.mpg.de>

N.Prymak, G. Kanbach, H. Steinle, A. Stefanescu, S. Duscha, F. Schrey, 
M. Muehlegger (MPE Garching) of the
OPTIMA-Burst Team report on optical observations of GRB060904b (BAT 
trigger Nr. : 228006; Circ.Nr. 5505, Grupe et al.):

OPTIMA-Burst at the 1.3m Skinakas Observatory, of the University of
Crete, Greece, observed the Swift/UVOT 0.5"-errorcircle of GRB060904b 
(GCN Circ. 5519, Oats et al.) on 2006 Sept. 04.
Relative photometry to several close-by USNO catalog stars (referenced 
by their R magnitude) was performed for the
detected optical transient in our unfiltered images of 25 second 
exposure each. Results are listed:

2006/Sept/04  post-BAT
 
start time(UT)  time(s)   R magnitude

02:39:25             502   16.90+-0.12
02:41:56             653   17.09+-0.16
02:44:00             777   17.24+-0.19
02:45:52             889   17.36+-0.17
02:47:47            1004   17.44+-0.14
02:48:56            1073   17.58+-0.14
02:55:29            1466   17.70+-0.22
02:56:01            1505   17.75+-0.20
02:58:52            1669   17.94+-0.18
03:00:14            1751   17.79+-0.21
03:01:05            1802   17.89+-0.14

Sorry for the delay, we didn't have Internet connection from Sept 2.5 to 
6.7.