[vsnet-grb-info 6462] GRB 080727B: Late VLT imaging

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8074
SUBJECT: GRB 080727B: Late VLT imaging
DATE:    08/08/06 05:38:15 GMT
FROM:    Thomas Kruehler at MPE/MPI  <kruehler at mpe.mpg.de>

T. Kruehler, J. Greiner (MPE Garching) and S. Klose (Tautenburg) report:

We triggered VLT/FORS imaging of the field of the Swift GRB 080727B
(Immler et al. 2008, GCN #8022). A series of exposures were obtained in
Rc (6*120s), Bessel I (5*120s) and Gunn z (4*120s) starting from 06:19 UT
on 2008-07-29, roughly 46 hours after the burst. We marginally detect the
optical afterglow (Li et al, 2008, GCN #8024) in the stacked I and z
frames at 24.7 +- 0.3 mag (I) and 23.9 +- 0.5 mag (z), calibrated
against USNO-B1 stars.

Given the large errors and the uncertain and high foreground extinction,
this is consistent with the power law reported in Kruehler et al (2008,
GCN #8045) and puts the upper redshift limit to ~5. The 3 sigma upper
limit in Rc (>25.5 mag) is above that power law and does not constrain
the shape of the spectral energy distribution or the redshift.

We thank the ESO/VLT staff for the perfect support.