{
  "bibcode": "2009GCN..9012....1T",
  "body": "C. C. Thoene (INAF-OAB), P. D'Avanzo (Univ. Bicocca & INAF-OAB), D.\nFugazza (INAF-OAB), A. de Ugarte Postigo (ESO), V. D'Elia, S. Piranomonte\n(INAF-OAR), S. Covino, S. Campana (INAF-OAB), G. Chincarini (Univ.\nBicocca) report, on behalf of the MISTICI collaboration:\n\nWe observed the optical afterglow of GRB 090313 (Chornock et al. GCN 8979;\nMao et al. GCN 8980) with the ESO VLT about 1.9 days after the burst with\nthe FORS2 camera in spectroscopic mode. We took 4 exposures of 20 min each\nwith the 600I grism covering the range 6800-9300 Angstrom with a\nresolution of R=1500.\n\nWhile we confirm the redshift reported by Chornok et al. (GCN 8994), we\nalso report the detection of a broad double absorption feature around\nobserved lambda 7830 and 7840 angstrom that does not fit any transition at\nthe GRB redshift (z = 3.375). This double feature can be interpreted as Mg\nII 2796,2803, each consisting of 2 velocity components with a separation\nof about 300 km/s, and could be a signature of an intervening system at\nz ~ 1.8. We cannot confirm the presence of Mg I 2852 at z = 1.8 due to the\npossible overlap with Mg I 1827 absorption at the redshift of the GRB.\n\nWe acknowledge excellent support from the ESO staff, in particular Yuri\nBeletsky.",
  "circularId": 9012,
  "createdOn": 1237503107000,
  "email": "paolo.davanzo@brera.inaf.it",
  "subject": "GRB 090313: VLT spectroscopy",
  "submitter": "Paolo D'Avanzo at INAF-OAB  <paolo.davanzo@brera.inaf.it>",
  "eventId": "GRB 090313"
}