T. Kruehler, S. Loew, J.Greiner, C.Clemens, A. Kuepcue Yoldas, A. Yoldas
(all MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 080129 observed by Swift (Immler et al.
2008, GCN#7226) simultaneously in grizJHK with GROND mounted at the 2.2m
MPI/ESO telescope at La Silla (Chile).
Observations started at 06:11 UT, about 4 min after the GRB.
We find a point source not present in the Digital Sky Survey images
inside the Swift/XRT error circle of the X-ray afterglow
(Perri et al. 2008, GCN#7228; Goad et al. 2008, GCN#7230).
The coordinates are (+- 0.5 arcsec error):
RA (2000.0) = 07h 01m 08.2s
Decl. (2000.0) = -07d 50' 47'
consistent with the optical source reported by J. S. Bloom (GCN#7229).
We estimate magnitudes of 22.8 (r), 21.5 (i), 20.6 (z), 18.9 (J), 18.1
(H) and 17.0 (K) calibrated against USNO and 2MASS field stars. These
magnitudes are not corrected for galactic extinction.
The source is fading by about 0.5 mag during the first 90 min, suggesting
it to be the optical/NIR afterglow of GRB 080129.