{
  "bibcode": "2020GCN.28739....1V",
  "body": "J.-B. Vielfaure (GEPI - Paris Observatory), D. Xu (NAO/CAS), J. Palmerio \n(GEPI - Paris Observatory), P. D'Avanzo (INAF-OAB), D. B. Malesani (DTU Space), \nJ. P. U. Fynbo (DAWN/NBI), V. D'Elia (ASI/SSDC), D. A. Kann (HETH/IAA-CSIC) and \nN. R. Tanvir (Univ. Leicester) report on behalf of the Stargate collaboration:\n\nWe observed the optical afterglow of GRB 201021C (Lien et al., GCN \n28730; Lipunov et al., GCN 28733) using the ESO VLT UT3 (Melipal) equipped \nwith the X-shooter spectrograph. Our spectra cover the wavelength range 3000-21000 AA, \nand consist of 4 exposures by 600 s each. The observation started at 03:29:00 UT on \n2020 Oct 22 (7.02 hr after the GRB).\n\nIn a 30 s image taken with the acquisition camera on Oct 22.14 UT, we detect the optical \nafterglow, for which we measure a magnitude r = 19.97 +/- 0.02 (AB, calibrated against \nnearby stars from the SkyMapper catalog; Wolf et al. 2018, PASA, 35, 010).\n\nWe clearly detect continuum over the whole X-shooter spectrum.\nFrom detection of multiple absorption features, which we interpret as \ndue to Si II, Al II, Al III, Fe II and Mg II, we infer a redshift z = 1.070.\nIn particular, weak fine structure lines from Fe II* are visible, which \nconfirm the association of the absorption system with the GRB. \nWe also detect Mg II and Mg I absorption features from an intervening \nsystem at z = 0.805. \n\n\nWe acknowledge excellent support from the ESO observing staff in \nParanal, in particular Bin Yang and Fernando Selman.",
  "circularId": 28739,
  "createdOn": 1603356359000,
  "email": "pda.davanzo@gmail.com",
  "subject": "GRB 201021C: VLT/X-shooter redshift",
  "submitter": "Paolo D'Avanzo at INAF-OAB  <pda.davanzo@gmail.com>",
  "eventId": "GRB 201021C"
}