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GCN Circular 2869

GRB041218, BVRcIc field calibration
2004-12-19T04:27:29Z (19 years ago)
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 11x11 arcmin field centered on the afterglow coordinates for the
INTEGRAL burst GRB041218 (Mereghetti et al., GCN 2858;
Torii GCN 2860, Gorosabel et al. GCN 2861)
with the USNOFS 1.0-m telescope on one marginally photometric
night.  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:
The astrometry in this file is based on linear plate solutions
with respect to USNOA2.  The external errors are less than 300mas.
The estimated external photometric error is about 0.04mag
due to the poor seeing, and will be improved with additional
calibration nights after Christmas.

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.
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