TITLE:   GCN CIRCULAR
NUMBER:  13730
SUBJECT: GRB 120909A: X-Shooter redshift 3.93
DATE:    12/09/09 05:22:52 GMT
FROM:    Olga Hartoog at U of Amsterdam  <O.E.Hartoog@uva.nl>

O. E. Hartoog (Uva, NL), D. Malesani (DARK/NBI), K. Wiersema (U. Leicester,
UK), T. Kruehler (DARK/NBI),  S. Schulze (PUC and MCSS), A. de Ugarte
Postigo (IAA/CSIC and DARK/NBI), V. D'Elia (INAF/Roma and ASI/ASDC), J. P.
U. Fynbo (DARK/NBI), report on behalf of the X-shooter GRB GTO
collaboration:

We observed the optical counterpart of GRB 120909A (Immler et al., GCN
13727; Haislip et al., GCN 13728; Sudilovsky et al., GCN 13729) with the
ESO VLT equipped with the X-shooter spectrograph. Observations were carried
out starting on 2012 Sep 9.14 UT (1.7 hr after the GRB), for a total
exposure time of 20 min, covering the wavelength range 3000-25000 AA.

We detect several absorption features, including Ly-a, FeII, NiII, SiII,
SII, AlII, AlIII, CII, OI, CIV, ZnII all at a common redshift z = 3.93. In
particular, the presence of fine-structure lines (Fe II*, SiII*, OI*, OI**,
CII*) makes the redshift securely associated to the GRB.

We acknowledge support from the VLT staff, in particular Giovanni Carraro
and Giacomo Beccari.