[vsnet-grb-info 6335] GRB 080707: GROND Confirmation of the Optical Afterglow

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7954
SUBJECT: GRB 080707: GROND Confirmation of the Optical Afterglow
DATE:    08/07/08 11:34:35 GMT
FROM:    Christian Clemens at MPE  <cclemens at 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 for a second time at 09:54 UT on July 8th, 
2008, 25.4 hr after the GRB trigger with 25.0 min of effective exposures in 
g'r'i'z'. The observations were performed at an average seeing of 1.6" and at 
an average airmass of 2.4.

We still detect the faint source mentioned in GCN #7948 within the 1.1'' 
Swift-UVOT error circle (Schady et al., GCN #7953) with the following 
preliminary magnitudes of

g' ~ 23.8 mag,
r' ~ 23.2 mag and
i' ~ 23.1 mag

and typical uncertainties of +/- 0.3 (calibrated against USNO-B1 field stars).

With a magnitude change of delta g' ~ 1.7 mag within 23.9 hr (similarily in r' 
and i' band) these measurements strongly suggest that the source mentioned in 
Clemens et al. (GCN #7948) is the afterglow of GRB 080707.