TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4184 SUBJECT: Recent GRB UBVRcIc field photometry DATE: 05/10/31 16:31:02 GMT FROM: Arne A. Henden at AAVSO A. Henden (AAVSO/USNO) reports on behalf of the USNO GRB Team: We have acquired UBVRcIc all-sky photometry for 23x23arcmin fields centered on the coordinates of recent GRB localizations with the USNOFS 1.0-m telescope on 1 or 2 photometric nights. We are using a new CCD, and so place an additional zeropoint error of about 0.03mag that should be added in quadrature to the errors reported in the files listed below. Stars brighter than V=13.0 are saturated and should be used with care. We have placed the photometric data on our anonymous ftp site: ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb050505.dat ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb051021.dat ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb051022.dat ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb051028.dat Since these bursts had identified optical afterglows, we may improve the photometric calibration on subsequent observing runs. As always, you should check the dates on the .dat file prior to final publication to get the latest photometry. There is a README file on the ftp directory to give you information about the procedures used to calibrate these fields.