GCN Circular 12431
Subject
GRB 111008A: VLT/X-shooter spectroscopy
Date
2011-10-09T11:03:04Z (13 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@dark-cosmology.dk>
K. Wiersema (Univ. Leicester), H. Flores (GEPI/Obs. de Paris), V. D'Elia
(ASI/ASDC & INAF/OAR), P. Goldoni (APC/Univ. Paris 7 & SAp/CEA), D.
Malesani (DARK/NBI), S. D. Vergani (INAF/OABr), A. de Ugarte Postigo
(IAA-CSIC), A. J. Levan (Univ. Warwick), B. Milvang-Jensen, J. P. U.
Fynbo (DARK/NBI), report on behalf of a larger collaboration:
We observed the optical counterpart of GRB 111008A (Saxton et al., GCN
12423; Levan et al., GCN 12426; Xu et al., GCN 12427; Nardini et al.,
GCN 12428), using the X-shooter spectrograph mounted on the ESO-VLT.
Observations started on 2011 October 9.247 UT (7.71 hr after the GRB),
with a total exposure time of 2 hr, covering the wavelength range
3000-25000 AA.
Continuum is clearly detected redwards of ~7600 AA, with several,
strong superimposed absorption features, consistent with a commom
redshift z = 4.9898. Among them, we note several Si II and Fe II
transitions, the CIV doublet, the Mg II doublet (in the H band), and
several fine-structure lines commonly observed in GRB afterglow spectra
(such as Si II*, S II*, O I*). We also note the presence of an
intervening Mg II system at z = 4.61. Our results are thus consistent
with the redshift derived by Levan et al. (GCN 12429; see also Nardini
et al., GCN 12428).
We acknowledge excellent support from the observing staff in Paranal, in
particular Christophe Martayan, Claudio Melo, Leonel Rivas, and Sergio Vera.