TITLE: GCN GRB OBSERVATION REPORT NUMBER: 1971 SUBJECT: GRB030131, BVRcIc field photometry DATE: 03/03/27 20:22:19 GMT FROM: Arne A. Henden at USNO/USRA A. Henden (USRA/USNO) reports on behalf of the USNO GRB team: We have acquired BVRcIc all-sky photometry for a 20x20 arcmin field centered at the candidate afterglow coordinates (Fox et al., GCN 1857) for the INTEGRAL burst GRB030131 (GCNs 1836, 1838, 1847) with the USNOFS 1.0-m telescope on one photometric night. Stars brighter than V=13.5 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/grb030131.dat The astrometry in this file is based on linear plate solutions with respect to UCAC2. The external errors are less than 100mas. The estimated external photometric error is 0.03mag. In particular, the star located at RA(J2000)=13:28:18.16 DEC(J2000)=30:38:20.79, used as a comparison star by Gorosabel et al. (GCN 1866) has B=18.95 +/- 0.03, making the OT fainter than what was given in that GCN. We will not be performing U-band calibration unless requested. As always, you should check the dates on the .dat file prior to final publication to get the latest photometry.