D.B. Fox, D.L. Kaplan, B. Cenko, and S.R. Kulkarni (Caltech), with
A. Nechita (Harvard), report on behalf of the Caltech-NRAO GRB
"We have observed the HETE-2 SXC localization region for XRF030723
(Prigozhin et al., GCN #2313) with the 60-inch and 200-inch (Hale)
telescopes on Mt. Palomar, on two successive nights commencing at
approximately July 24.4 UT and July 25.4 UT. 60-inch observations
were made in R-band with CCD13; 200-inch observations were made in
Ks-band with WIRC. We have photometered these data against the USNO
and 2MASS catalogs; limiting magnitudes for our exposures are
approximately R~22.8 and Ks~19.4 on July 24.5 UT (mean epoch), and
R~22.5 and Ks~19.0 on July 25.5 UT, respectively.
"Comparison of the two epochs of R-band imaging reveals a stationary,
point-like, fading source with magnitudes R~21.3 on July 24.5 and
R~22.4 (near the limit of detection) on July 25.5. This source is
also detected in our July 24.5 Ks-band image with Ks~18.65; it is not
detected in our July 25.5 Ks-band image to the Ks~19.0 limit. The
coordinates of the source, referenced to the GSC 2.2, are:
RA 21:49:24.40, Dec -27:42:47.4 (J2000)
with an uncertainty of less than 0.5" in each coordinate.
Given the pronounced fading of the source we suggest that it is likely
to be the optical counterpart of XRF030723.
Images of the field and proposed counterpart will be provided soon at