TITLE:   GCN CIRCULAR
NUMBER:  9942
SUBJECT: GRB 090926A: VLT/X-shooter redshift
DATE:    09/09/27 06:48:04 GMT
FROM:    Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst  <malesani@astro.ku.dk>

D. Malesani (DARK/NBI), P. Goldoni (APC/Univ. Paris 7 and SAp/CEA), J. 
P. U. Fynbo (DARK/NBI), V. D'Elia (ASDC and INAF/OAR), S. Covino 
(INAF/OABr), H. Flores (Paris Obs.), A.J. Levan (Univ. Warwick), S. D. 
Vergani (APC/Univ. Paris 7), K. Wiersema (Univ. Leicester), report on 
behalf of the X-shooter GRB collaboration:

We observed the afterglow of GRB 090926A (Bissaldi, GCN 9933; Uehara et 
al., GCN 9934; Vetere et al., GCN 9936; Haislip et al., GCN 9937) with 
the X-shooter spectrograph mounted on the ESO-VLT UT2. Observations were 
taken as part of the instrument Science Verification phase. X-shooter is 
a broad-band single-object spectrograph covering the wavelength range 
from the UV to the infrared (3300-22000 AA).

At the beginning of the observation (22.0 hr after the GRB), the 
afterglow had R = 17.9 as measured from the acquisition image. Four 
spectra lasting 1800 s each were secured.

The spectrum has high signal to noise and shows a wealth of absorption 
features, together with a broad depression around 3780 AA, which we 
interpret as a DLA. We identify CIV 1548 and 1550, Si II 1304 and 1526, 
SiII* 1533, FeII 1608, MgII 2798 and 2803, and several others, from 
which we measure a redshift z=2.1062. We caution that the wavelength 
solution is based on archival calibration data.

We thank the ESO observing staff, in particular Joel Vernet, Thomas 
Bensby, and Stephane Brillant.