TITLE:   GCN CIRCULAR
NUMBER:  998
SUBJECT: GRB010222: Optical observation and decay
DATE:    01/03/01 09:21:10 GMT
FROM:    Christian Veillet at CFHT  <veillet@cfht.hawaii.edu>

The optical counterpart of GRB010222 has been observed using the
CFHT Multi Object Spectrograph in imaging mode at the Cassegrain
focus of the 3.6-m CFH Telescope on the night of Feb. 27 to 28.

One image was obtained in relatively poor conditions (seeing ~ 1.5").
A preliminary reduction using stars (223.008250,43.006507) and
(223.098277,42.994077) from Henden's list (GCN #987) gives:

Feb. 28.653 UTC   R = 22.60 +/- 0.15

The relative photometry of the two stars used is consistent 
with our image within 0.02 magnitudes. Using all the measurements
of the R magnitude of the OT published in the GCN's (corrected if 
needed to put them back in the photometric system of Henden's list),
the R magnitude is following a nice power law decay with an index of
1.20 +/- 0.07 since 0.6 days after the burst.

An image of the OT and a graph of the decay are available at
http://www.cfht.hawaii.edu/~veillet/grb.html

S. Lilly and J. McDonald are acknowledged for their help in
this observation.

This message may be cited.
-- 
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Dr. Christian Veillet,       CFHT Senior Resident Astronomer
Phone: (808) 885-3161   http://www.cfht.hawaii.edu/~veillet/
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