TITLE:   GCN CIRCULAR
NUMBER:  7948
SUBJECT: GRB 080707: GROND Detection of the Optical Afterglow Candidate
DATE:    08/07/07 12:01:41 GMT
FROM:    Christian Clemens at MPE  <cclemens@mpe.mpg.de>

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

We observed the field of GRB 080707 (Swift trigger 316204; Schady et al., GCN 
#7947) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 
120, 405) mounted at the 2.2 m ESO/MPI telescope at La Silla Observatory 
(Chile).

Observations started at 10:00 UT on July 7th, 2008, 92.2 min after the GRB 
trigger, and were performed at an average seeing of 2.2" and at an average 
airmass of 2.6.

We found a faint source within the 2.9'' Swift-XRT error circle at

RA (J2000.0) = 02h 10m 28.40s
DEC (J2000.0) = +33d 06' 34.3''

with an uncertainty of 0.8".

The object is detected in g' band, implying a redshift smaller than 3.5.

Based on the first 4.4 min of effective exposures in g'r'i'z', we estimate 
preliminary magnitudes of

g' ~ 22.1 mag,
r' ~ 21.5 mag,
i' ~ 21.4 mag and
z' ~ 21.2 mag

with typical errors of +/- 0.3. Given magnitudes are calibrated against 
USNO-B1 field stars.

Please note, that no correction for the galactic foreground reddening of 
E(B-V) = 0.1 mag (Schlegel et al., 1998) has been applied.