GCN Circular 7949
Subject
GRB 080707: VLT redshift
Date
2008-07-07T12:42:24Z (16 years ago)
From
Daniele Malesani at Niels Bohr Inst,Dark Cosmology Center <malesani@astro.ku.dk>
Johan P. U. Fynbo, Daniele Malesani, & Bo Milvang-Jensen (DARK), report
on behalf of a larger collaboration:
We observed the field of GRB 080707 (Schady et al., GCN 7947) with the
ESO VLT equipped with FORS1.
Inside the XRT error circle, we detect the object first reported by
Clemens et al. (GCN 7948) in the R and I bands. The source had R ~ 19.6
on 2008 Jul 7.385 UT (47 min after the trigger), calibrated against
USNO-B1. This object is not visible in the DSS (which reaches a deeper
limit) and seems brighter than in the later observation reported by
Clemens et al. (GCN 7948). It is thus very likely the optical afterglow
of GRB 080707. A finding chart is posted at
http://www.astro.ku.dk/~malesani/GRB/080707/080707_finder.jpg
FORS1 spectra were acquired between Jul 7.397 and 7.441 UT with grism
300V. From detection of FeII and MgII absorption features, we infer a
redshift z = 1.23. A conservative upper limit z < 2.2 can be set from
the lack of Lyman alpha forest in the blue
We acknowledge excellent and enthusiastic support from the observing
staff at Paranal, in particular Chris Lidman, Lorena Faundez, Claudia
Reyes, and Dominique Naef.
[GCN OPS NOTE(07jul08): The two occurances of "GCN 7984" was changed
to "GCN 7948".]
