[vsnet-grb-info 6205] GRB 080605: GROND detection of the optical afterglow candidate

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7834
SUBJECT: GRB 080605: GROND detection of the optical afterglow candidate
DATE:    08/06/06 04:30:38 GMT
FROM:    Christian Clemens at MPE  <cclemens at mpe.mpg.de>

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.