TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  2801
SUBJECT: GRB041006, BVRcIc field calibration
DATE:    04/10/13 16:59:46 GMT
FROM:    Arne A. Henden at USNO/USRA  <aah@nofs.navy.mil>

A. Henden (USRA/USNO) reports on behalf of the USNO GRB team:

We have acquired BVRcIc all-sky photometry for
a 11x11 arcmin field centered on the afterglow coordinates
(da Costa et al., GCN 2765; Yamaoka et al., GCN 2781)
for the HETE burst GRB041006 (trigget 3570; Galassi et al., GCN 2770)
with the USNOFS 1.0-m telescope on one marginally 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/grb041006.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 about 0.03mag
and will be improved with additional calibration nights
later this week.

In particular, the stars calibrated by Fugazza et al. (GCN 2782)
and da Costa and Noel (GCN 2789) are present in the file, with
similar magnitudes within error.

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.