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GCN Circular 6601

Subject
GRB 070611: VLT observations
Date
2007-07-06T09:59:43Z (16 years ago)
From
Pall Jakobsson at U Hertfordshire <P.Jakobsson@herts.ac.uk>
Pall Jakobsson (U. Hertfordshire), Daniele Malesani,
Dong Xu, Johan P.U. Fynbo, Jens Hjorth and Christina
C. Thoene (DARK, NBI) report:

Using FORS1 on the Very Large Telescope during
non-photometric conditions, we obtained a total of
4200 s R-band imaging of the GRB 070611 field
(Stroh et al., GCN 6494) on June 15.375 (4.26 days
after the burst). On the edge of the refined XRT circle
(Butler 2007, AJ, 133, 1027; DSS catalog; version 3.6),
we clearly detect a source that is consistent with the
UVOT position (Landsman et al., GCN 6504).

Compared to the acquisition image obtained on June 11.040
(7.58 hr post-burst; Thoene et al., GCN 6499), the source
has faded by dm = 5.3 +/- 0.3 mag. If the optical afterglow
displays a similar fading behaviour as the X-ray afterglow
with a possible jet-break around 1 day (Stroh et al.,
GCN Report 63.3), we would expect dm = 3.5 +/- 1.4 mag.
Thus, the VLT observations are marginally consistent with a
break occurring in the optical band as well.

We note that the source is somewhat extended at the latter
epoch, implying that the host might contribute to the flux
and hence the observed dm could be larger. An image of the
field (on June 15.375) is shown at:

http://star-www.herts.ac.uk/~palli/grb070611/grb070611.jpg
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