T. Kruehler, J. Greiner, F. Schrey, G. Sala, C. Clemens (all MPE Garching)
report on behalf of the GROND team:
We observed the field of the INTEGRAL GRB 080723B (Gotz et al. 2008,
GCN #8002) on two epochs, simultaneously in g'r'i'z'JHK with GROND
(Greiner et al. 2008, PASP 120, 405) mounted at the 2.2m ESO/MPI telescope
at La Silla Observatory (Chile). First observations started at
2008-07-24 23:46 UT, 36.4 h after the burst, with total exposures of
50 min in g'r'i'z' and 40 min in JHK. A second set of images was obtained
starting at 2008-07-31 23:39 UT with effective exposures of 100 min
(g'r'i'z') and 80 min (JHK).
We do not detect a fading source in neither the XRT (Page 2008, GCN #8008)
nor XMM (Sala et al. 2008, GCN #8078) error circle down to limiting
g' > 23.4
r' > 23.6
i' > 22.7
z' > 22.7
J > 20.6
H > 19.5
K > 18.5
calibrated against USNO-B1 and 2MASS field stars. At longer wavelength,
these limits are compromised by the high density of foreground stars.
The reported upper limits are not corrected for the expected Galactic
foreground extinction corresponding to a reddening of E_(B-V) = 1.3
(Schlegel et al. 1998).