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GCN Circular 967

GRB010222, optical observations
2001-02-22T21:04:26Z (23 years ago)
Arne A. Henden at USNO/USRA <>
A. Henden (USRA/USNO) and F. Vrba (USNO), on behalf of the
USNO GRB team and a larger European GRB collaboration, report:

We observed the BeppoSAX error box for GRB010222 (GCN 959, 960, 966)
with the USNOFS 1.0-m telescope under cloudy conditions.
The discovery of the optical transient for this burst
was given in Henden (GCN 961, 962).  The final astrometry for
the OT, relative to USNO-A2.0, is

223.05229     43.01840
14:52:12.55  +43:01:06.2  (J2000)

with internal errors of 0.2arcsec.  This is in agreement
with the values given in McDowell et al. (GCN 963).

A finding chart (R-band, 4.5x4.5arcmin, NE=upperleft) is given at

BVRcIc frames were taken shortly after the localization
posting.  However, only the preliminary R-band measures
are reported here.  The quality of the photometry suffered
due to the thick clouds, but is good enough to show definite
fading of the transient:

  UT        exp      Rc    err
010222.486  1x300  18.36  0.059
010222.510  2x300  18.52  0.054
010222.518  2x600  18.68  0.059
010222.533  2x600  18.67  0.057

Where the R-band magnitudes are relative to the bright USNO-A2.0
star (identified as "A" on the finding chart) at J2000 coordinates
14:52:14.80 +43:01:40.9 and that has an assumed magnitude R=14.70.

More careful all-sky calibration of this field will be performed
on the next few nights.  The intent is to only calibrate in
BVRcIc; please contact Henden if you need U-band calibration as well.
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