{
  "bibcode": "2007GCN..6851....1F",
  "body": "D. Fugazza (INAF-OABr), F. Fiore, V. D'Elia (INAF-OAR), P. D'Avanzo \n(INAF-OABr), S. Piranomonte, L.A. Antonelli (INAF-OAR), G. Chincarini \n(Univ. Bicocca), S. Covino, G. Tagliaferri (INAF-OABr), M. Della Valle \n(INAF-OAA), A. Fernandez Soto (Univ. Valencia) report on behalf of the \nMISTICI collaboration:\n\nWe observed the optical afterglow of GRB 071003 (Schady et al., GCN \n6837; Li et al. GCN 6838; Cenko et al. GCN 6839) with the ESO-Very Large \nTelescope equipped with the FORS2 camera in spectroscopic mode. We took \na 1800s spectrum with the grism 600B (with a resolution of R = 780) on \nOct 04.055 UT (~ 0.735 days after the burst), under good seeing \nconditions (1.0\").\n\nThe detection of a MgII system at z=1.100 (Perley et al. GCN 6850), \ncannot be confirmed by our data, because the 2803 AA component of the \nMgII doublet is contamined by the NaI 5891 and 5897 AA doublet of the \nnearby bright star.\n\nWe also find significant lines at 5417 and 5430 AA, which we interpret \nas the MgII absorption doublet at 2797 and 2803 AA at z=0.937. FeII 2382 \nis also detected at the same redshift.\n\nIn addition, we find two more significant absorption lines (5417 and \n5446 AA), that can be identified as Ca H and K at z=0.372. \nAlternatively, the 5446 AA line can be interpreted as the  2803 AA \ncomponent of the MgII doublet at z=0.942, with the 2797 AA component \nsharing the absorption feature at 5430 AA with the MgII 2803 of the \nsystem at z=0.937. This can be another line-locking example like that of \nthe CIV system of GRB 021004 at z=2.3 (Fiore et al. 2005, ApJ, 624, 853; \nStarling et al. 2005, MNRAS, 360, 305 ).\n\nFinally, we find another MgII doublet at ~4000 AA (z=0.370), not \nconsistent with the Ca system at z=0.372. No emission lines are visible.\n\nIn summary our analysis of the FORS2 spectrum puts a lower limit on the \nredshift of GRB 071003 to z=0.937.\n\nWe thank VLT staff for performing the observations, in particular Thomas \nSzeifert and Alain Smette.",
  "circularId": 6851,
  "createdOn": 1191605414000,
  "email": "paolo.davanzo@brera.inaf.it",
  "subject": "GRB 071003: VLT spectroscopy",
  "submitter": "Paolo D'Avanzo at INAF-OAB  <paolo.davanzo@brera.inaf.it>",
  "eventId": "GRB 071003"
}