TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1564
SUBJECT: GRB021004: Optical Afterglow
DATE:    02/10/04 15:12:59 GMT
FROM:    Derek Fox at CIT  <derekfox@astro.caltech.edu>

D.W. Fox reports on behalf of the Caltech-NRAO GRB Collaboration:  

"We have observed the error box of GRB021004 (HETE Trigger 2380;
trigger time 12:06:13.57 UT) with the 48-inch Oschin/NEAT robotic
telescope at Palomar Observatory, with three 60-second integrations
beginning at 12:15:11, 12:17:45, and 12:22:52 UT.  We identify a new,
stationary, fading, point-like object by comparison with the Digitized
Sky Survey.  The object coordinates are:

    RA 00:26:54.689, Dec +18:55:41.3   (J2000)

with an uncertainty of less than 0.5" in each coordinate.  Deriving an
R-band photometric zero-point for our unfiltered observations by
reference to the USNO star at 00:26:58.713 +18:56:56.61, which we
assume to have magnitude R=15.3, we find object magnitudes at our
three mean epochs of:

         Mean Epoch  
       UT      From GRB   Magnitude
  ========================================
    12:15:41 UT   567 s   15.34 mag
    12:18:15      721     15.49
    12:23:22     1028     15.78
  ========================================

Given the source brightness and fading behavior we identify the object
as the likely optical afterglow of GRB021004.  A finding chart from
these observations may be found at

    http://www.astro.caltech.edu/~derekfox/grb021004/finder.ps.gz

and a web page presenting the observations will be available soon at
http://www.astro.caltech.edu/~derekfox/grb021004/."