{
  "bibcode": "2010GCN.10495....1V",
  "body": "S.D. Vergani (APC/Univ. Paris 7), P. D'Avanzo (INAF-OAB), D. Malesani, \nJ.P.U. Fynbo, J. Hjorth (DARK/NBI), A.J. Levan (Univ. Warwick), H. Flores\n(Paris Obs.), N.R. Tanvir (Univ. Leicester), P. Goldoni (APC/Univ. Paris 7\nand SAp/CEA), L.A. Antonelli (INAF-OAR) report on behalf of a larger\ncollaboration:\n\nWe observed the optical afterglow of GRB 100316B (Baumgartner et al., GCN\n10489; Afonso et al. GCN 10493; Haislip et al., GCN 10494) with the VLT\nequipped with the X-shooter spectrograph. Observations started on 2010 Mar\n16 at 08:43 UT (~ 40 minutes after the GRB), for a total exposure time of\n4x600 s. From the acquisition image, we estimate for the optical afterglow\na magnitude of R = 18.2 +- 0.1 (calibrated against USNO-B1.0).\nIn a preliminary analysis of the specta, we clearly detect the continuum\nin the UVB, VIS, and NIR arms, corresponding to the wavelength range\n3200-24000 AA. We detect several absorption features, among these\nFeII(1608), AlII(1670), AlIII(1854), FeII(2344), FeII(2374), FeII(2382),\nMgII(2796, 2803) and MgI(2852) at a common redshift of z=1.180. The lack\nof Lyman forest lines down to ~3200 AA sets an upper limit to the redshift\nz<1.6. We also find evidence for FeII lines and MgII doublet from a strong\nintervening systems at z=1.063.\n\nWe caution that the above analysis (particularly the wavelength solution)\nis preliminary. Reduction with updated calibrations is underway. We would\nlike to thank the ESO staff for their kind assistance, in particular Linda\nSchmidtobreick, Christophe Martayan, Patricia Guajardo and Manuel\nOlivares.",
  "circularId": 10495,
  "createdOn": 1268737499000,
  "email": "paolo.davanzo@brera.inaf.it",
  "subject": "GRB 100316B: VLT/X-shooter redshift",
  "submitter": "Paolo D'Avanzo at INAF-OAB  <paolo.davanzo@brera.inaf.it>",
  "eventId": "GRB 100316B"
}