[vsnet-grb-info 3484] GRB 060708: VLT spectroscopy

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  5319
SUBJECT: GRB 060708: VLT spectroscopy
DATE:    06/07/15 01:57:00 GMT
FROM:    Pall Jakobsson at U Hertfordshire  <palli at star.herts.ac.uk>

Pall Jakobsson (U. Hertfordshire), Paul Vreeswijk (ESO),
Sara Ellison (U. Victoria), Javier Gorosabel (IAA-CSIC Granada),
Nial Tanvir (U. Hertfordshire), Johan P.U. Fynbo, Brian L. Jensen,
Jens Hjorth (DARK, NBI), D. Alexander Kann (TLS Tautenburg),
Klaas Wiersema and Ralph A.M.J. Wijers (University of Amsterdam)
report on behalf of a larger collaboration:

Using FORS2 on the Very Large Telescope, we have obtained 3*30 min
spectra (300V) of the GRB 060708 field (Moretti et al., GCN 5292).
The UVOT optical afterglow candidate (Moretti et al., GCN 5292;
Schady & Moretti, GCN 5296) has clearly faded in our acquisition
image. Using photometric zeropoints from the ESO webpages we
estimate the afterglow magnitude to be R ~ 22.9 on July 10.290
(1.778 days post-burst).

The combined spectrum does not display any obvious features. However,
a firm upper limit of z < 2.3 can be placed on the redshift of
GRB 060708 from the lack of Ly-alpha forest lines in the spectrum
of the afterglow. This is consistent with the UVOT observations
(Schady & Moretti, GCN 5296).

The slit was aligned to cover the galaxy, 8 arcsec south of the
afterglow (just outside the XRT error circle). This galaxy has a
magnitude of R ~ 19.5 and displays numerous absorption features,
such as Ca II (K & H), G-band, H-beta, Mg I, Na I (D) and H-alpha,
corresponding to a redshift of z = 0.249.

An image of the field is shown at:

http://star-www.herts.ac.uk/~palli/grb060708/grb060708.jpg