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GCN Circular 1301

GRB020322 BVRI field photometry
2002-03-23T18:25:03Z (22 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
an 11x11 arcmin field that is approximately centered on
the position of the candiate optical transient reported
by Bloom et al. (GCN 1296) 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:
The conditions were basically clear, but with weather maps
indicating passing clouds over the northern horizon in the direction
of the GRB field.  There is a slight possibility that the
photometry has larger than the expected 0.02mag external
error, but all tests (such as color consistency) seem reasonable.
The astrometry in this file is based on linear plate solutions
with respect to USNO-A2.0.  The internal errors are less than 100mas.

In particular, the USNO-A2.0 star at 18:00:58.03, +81:06:08.3
that was used to calibrate their field can be found in the .dat file
with the following magnitudes:
  B = 19.42  V = 18.12  R = 17.30  I = 16.59
with estimated photometric errors of about 2 percent, including
the known zeropoint errors quoted above.

Further calibration of this field will be performed when
weather conditions improve and moonlight decreases.
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