{
  "bibcode": "2007GCN..6398....1J",
  "body": "Pall Jakobsson (U. Hertfordshire), Johan P. U. Fynbo (DARK, NBI), \nMichael I. Andersen (Potsdam), Andreas O. Jaunsen (U. Oslo),\nChristina C. Thoene, Darach Watson, Jens Hjorth, Bo Milvang-Jensen\n(DARK, NBI), Nial R. Tanvir (U. Leicester) and P. Moller (ESO) \nreport on behalf of a larger collaboration:\n\nUsing FORS1 on the Very Large Telescope, we have obtained 3*30 min \nspectra (grism 300V) of GRB 070508 (Grupe et al., GCN 6383). The \nUVOT optical afterglow candidate (Marshall & Grupe, GCN 6392) has \nclearly faded in our acquisition image. Using photometric zeropoints \nfrom the ESO webpages we estimate the afterglow magnitude to be\nR ~ 22.0 on May 8.337 (3.79 hours post-burst).\n\nThe combined spectrum does not display any obvious absorption \nfeatures. However, a firm upper limit of z < 2.3 can be placed on \nthe redshift of GRB 070508 from the lack of Ly-alpha forest lines in \nthe spectrum of the afterglow. This is consistent with the UVOT \nobservations (Marshall & Grupe, GCN 6392).\n\nWe do detect a tentative emission line at 6781 A. If it corresponds \nto H-alpha at z = 0.033, we would expect to detect H-beta and the \n[O III] doublet in our spectrum. However, no features are visible \nat their predicted locations. The most probable association is with \n[O II] 3728, corresponding to a redshift of z = 0.82. We caution\nthat the magnitude reported above is then most likely affected by\nhost galaxy emission.\n\nWe thank the Paranal staff for excellent support.",
  "circularId": 6398,
  "createdOn": 1178723462000,
  "email": "P.Jakobsson@herts.ac.uk",
  "subject": "GRB 070508: OA fading and tentative redshift",
  "submitter": "Pall Jakobsson at U Hertfordshire  <P.Jakobsson@herts.ac.uk>",
  "eventId": "GRB 070508"
}