{
  "bibcode": "2012GCN.12991....1W",
  "body": "K. Wiersema (Leicester), P. Goldoni (APC/Univ. Paris 7 and SAp/CEA), J. P.\nU. Fynbo (DARK/NBI), N. R. Tanvir (U. Leicester), D. Malesani (DARK/NBI),\nA. de Ugarte Postigo (IAA-CSIC, DARK/NBI), S. D. Vergani (INAF/OAB), S.\nCovino (INAF/OAB), H. Flores (Obs. Paris) report on behalf of the\nX-shooter GTO GRB collaboration:\n\nWe observed the position of the afterglow of GRB 120224A (Saxton et al.,\nGCN 12980) using the X-shooter spectrograph mounted on the VLT.\nObservations started on 00:30 UT on 25 February 2012, i.e. 19.83 hours\nafter burst.\nIn the acquisition images, 5 x 150 seconds in R filter, we find a faint\nsource, consistent with the candidate afterglow reported by Elliott et al\n(GCN 12988). We find a preliminary magnitude of R=22.3 using the USNO-B\nstar 0722-0043411 (R=16.65). The detection of the afterglow in the R band\nplaces a limit on the redshift of approximately z < 5.\n\nWe performed spectroscopy of this source, under poor seeing and high\nairmass. We detect a faint continuum in the near-infrared arm over the\nwhole wavelength range, at low signal to noise.\nIn the visual arm data we detect a very faint continuum at the red end of\nthe wavelength range. No emission lines are detected. Because of the low\nsignal to noise we are not able to identify absorption features. The non-\ndetection of continuum emission below ~600 nm may be indicative of a\nmoderately high redshift for this burst, though alternatives, such as a\nreddened spectrum (note that the X-ray afterglow shows considerable\nabsorption; Osborne et al. GCN 12986), can not be excluded at present.\n\nWe are grateful for the excellent support from the Paranal Observatory\nstaff, in particular Myriam Rodrigues and Ivo Saviane.",
  "circularId": 12991,
  "createdOn": 1330379120000,
  "email": "kw113@leicester.ac.uk",
  "subject": "GRB 120224A: VLT/X-shooter observations",
  "submitter": "Klaas Wiersema at U Leicester  <kw113@leicester.ac.uk>",
  "eventId": "GRB 120224A"
}