GCN Circular 7834

C. Clemens, T. Kruehler, J. Greiner, A. Kupcu Yoldas, A. Yoldas (all MPE 
Garching) and G. Szokoly (Eoetvoes Univ., Budapest and MPE Garching) report 
on behalf of the GROND team:

We observed the field of GRB 080605 (Swift trigger 313299; Sbarufatti et al., 
GCN #7828) 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).

Observations started at 01:10:59 UT on June 6th, 2008, 83 mins after the GRB 
trigger, and are continuing.

We found a single and relatively bright point source within the 1.0'' 
Swift-UVOT error circle reported by Holland et al. (GCN #7830) at

RA (J2000.0) = 17h 28m 30.05s
DEC (J2000.0) = +04d 00' 56.2"

with a typical uncertainty of 0.8", which is consistent with the sources 
reported by Kann et al. (GCN #7829) and Gomboc et al. (GCN #7831).

Based on 460 s and 1500 s of effective exposures taken 1.65 hrs and 2.78 hrs 
after the trigger, we estimate preliminary magnitudes of

r' = 20.3 and i' = 19.4, as well as
r' = 20.7 and i' = 19.9

with typical errors of +/- 0.1. (Given magnitudes are calibrated against 
USNO-B1 field stars and might be affected by the bright, nearby star.)

This indicates a clear fading of the source, which we therefore suggest to be 
the optical afterglow of GRB 080605.