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GCN Circular 1916

GRB030226, BVRcIc field calibration
2003-03-03T18:04:13Z (21 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 20x20 arcmin field centered at the coordinates
for the optical transient (Fox et al., GCN 1879)
associated with the HETE burst GRB030226 (Suzuki et al., GCN 1888)
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:
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 two comparison stars listed by Garnavich,
et al. (GCN 1885) can be found in this file with Rc magnitudes:
   ID    Garnavich   Henden
Star A    15.39     15.45
Star B    17.06     17.05
In agreement within the quoted errors.

This calibration will be extended with additional nights to
ensure against a systematic zeropoint error, but current
weather forecasts indicate that this may be a week or two.
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.
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