GCN Circular 9942
Subject
GRB 090926A: VLT/X-shooter redshift
Event
Date
2009-09-27T06:48:04Z (16 years ago)
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.