TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4120
SUBJECT: GRB 051021: Optical observations and candidate afterglow
DATE:    05/10/21 16:59:15 GMT
FROM:    Derek Fox at PSU  <dfox@astro.psu.edu>

D.B. Fox (Penn State), with R. McNaught and B. Peterson (RSAA/ANU),
report on behalf of a larger collaboration:

"We have observed the HETE localization region for GRB051021 (Yoshida
et al., GCN 4116) with the 40-inch telescope at Siding Spring
Observatory, in a sequence of R-band exposures beginning at 13:48:48
UT (26m51s after the burst).  Comparison of a coadded image with mean
epoch 14:34:33 (1h12m post-burst) to the Digitized Sky Survey reveals
the presence of a new R~18.5 mag source, at coordinates:

     R.A. 01:56:36.39, Dec +9:04:03.7  (J2000)

with a coordinate uncertainty, relative to USNO-B1.0 catalog
astrometry, of <0.5".  Inspection of our individual images suggests
fading of the source over the ~1 hour span of our observations.
However, in the absence of a more sophisticated reduction of these
data it is not possible to make a firm conclusion as to variability at
this time.  Moreover, the presence of a cosmetic defect at the source
position in one image introduces significant uncertainty to our
mean photometric estimate, above.

We suggest that this source may be the optical afterglow of
GRB051021."