{
  "bibcode": "2018GCN.23356....1F",
  "body": "Johan P. U. Fynbo (DAWN/NBI and DAWN/DTU), Antonio de Ugarte Postigo \n(HETH/IAA-CSIC and DARK/NBI), Valerio D'Elia (ASI-SSDC), Nial R. Tanvir \n(Univ. Leicester), Giovanna Pugliese (API/Univ. Amsterdam), D. Alexander \nKann (HETH/IAA-CSIC), D. Malesani (DAWN/NBI, DAWN/DTU, and DARK/NBI), \nand Kasper E. Heintz (Univ. Iceland), report on behalf of the Stargate \ncollaboration:\n\nWe observed the optical afterglow of the bright Swift and Fermi GRB \n181020A (Moss et al., GCN 23349; Axelsson, GCN 23350; Veres, GCN 23352) \nwith the ESO VLT UT2 equipped with the X-shooter instrument. \nSpectroscopy covering the wavelength range 3000-21000 AA was carried out \nstarting on 2018 Oct 21.030 UT (5.7 hr after the GRB), for a total of \n4x600 s exposure time.\n\nIn a 5-s image taken with the acquisition camera on 2018 Oct 10.023 UT, \nwe measure for the afterglow R ~ 17.3 (Vega), assuming R = 18.34 for the \nUSNO star at RA = 00:55:51.53, Dec = -47:23:14.5.\n\nThe spectrum has a very high S/N. A wide trough is easily visible around \n4780 AA, which we interpret as a DLA in the GRB host system. From \ndetection of a plethora of absorption lines, including Al II, Al III, S \nII, O I, Si II, Si IV, C IV, Zn II, Cr II, Ni II, Fe II, Mn II, O I*, Si \nII*, Ni II*, Fe II*, we measure the redshift to be z = 2.938. The \nvelocity structure of the lines spans the redshift range 2.9360-2.9407 \n(2.938 corresponding to the strongest component). The detection of \nfine-structure lines makes the redshift association with the GRB host \nsystem secure. Intervening absorbers are also detected at z = 1.788 (Mg \nII), 2.172 (Mg II), and 2.822 (C IV).\n\nWe acknowledge the ESO observing staff in Paranal for conducting these \nobservations, in particular Elizabeth Bartlett, Stephane Brillant, \nMarcelo Lopez, and Thomas Rivinius.",
  "circularId": 23356,
  "createdOn": 1540116542000,
  "email": "malesani@dark-cosmology.dk",
  "subject": "GRB 181020A: VLT/X-shooter spectroscopy and redshift",
  "submitter": "Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst  <malesani@dark-cosmology.dk>",
  "eventId": "GRB 181020A"
}