{
  "bibcode": "2014GCN.15645....1X",
  "body": "D. Xu (DARK/NBI), D. Malesani (DARK/NBI), N. R. Tanvir (Univ. \nLeicester), V. D'Elia (ASI/ASDC), A. de Ugarte Postigo (IAA/CSIC and \nDARK/NBI), T. Kruehler (ESO), J. P. U. Fynbo (DARK/NBI) report on behalf \nof a larger collaboration:\n\nWe observed the optical counterpart of the Fermi/LAT GRB 131231A (Sonbas \net al., GCN 15640; Jenke & Xiong, GCN 15644; Xu et al., GCN 15641) with \nthe ESO VLT equipped with the X-shooter spectrograph. The mean time of \nour observation is 2014 Jan 1.04 UT, that is 20.2 hr after the GRB. The \nspectrum covers the wavelength range 3200 to 18,000 AA.\n\nThe trace of the afterglow is well visible in all arms. We detect \nseveral absorption features which we interpret as due to Fe II, Mg II, \nCa H and K, all at a common redshift z = 0.642 (wavelength solution \nbased on archival calibration lamps). Emission lines corresponding to \nthe [O III] doublet are also detected at the same redshift.\n\nWe acknowledge excellent support from the observing staff in Paranal, in \nparticular Steffen Mieske.",
  "circularId": 15645,
  "createdOn": 1388543770000,
  "email": "malesani@dark-cosmology.dk",
  "subject": "GRB 131231A: VLT/X-shooter redshift",
  "submitter": "Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst  <malesani@dark-cosmology.dk>",
  "eventId": "GRB 131231A"
}