{
  "bibcode": "2013GCN.14478....1X",
  "body": "D. Xu (DARK/NBI), A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), S.\nSchulze (PUC and MCSS), J. Jessen-Hansen (AU), G. Leloudas (OKC,\nStockholm), T. Kruehler, J.P.U. Fynbo (DARK/NBI), P. Jakobsson (U.\nIceland) report on behalf of a larger collaboration:\n\nWe observed the field of GRB 130427A (Maselli et al., GCN 14448) with\nthe 2.5m Nordic Optical Telescope (NOT) equipped with the ALFOSC\ncamera. Observations started at 20:39:12 UT on 2013-04-27 (i.e., 12.85\nhr after the BAT trigger).\n\nWe first obtained a series of frames in the sloan u-, g-, r-, i-, and\nz-band filters. The optical afterglow (ref., Elenin et al., GCN 14450)\nis clearly detected in the stacked images in each of these filters.\nPreliminary analysis gives the following magnitudes\n\nu=17.70+/-0.03\ng=17.34+/-0.03\nr=17.07+/-0.03\ni=16.94+/-0.03\nz=16.88+/-0.03\n\nat a mean time of 12.96 hr post-trigger, calibrated with nearby stars\nin the SDSS field.\n\nWe also carried out a 1800s spectroscopic exposure. The spectrum\ncovers 3200 - 9100 AA at a resolution of ~700 and has a high S/N. We\ndetect prominent absorption lines of the MgII doublet, MgI and CaII K\n& H as well as weak emission lines of the [OII] doublet and H-beta,\nall at a common redshift of z=0.338+/-0.002, consistent with the\nredshift reported by Levan et al. (GCN 14455).",
  "circularId": 14478,
  "createdOn": 1367110049000,
  "email": "dong.dark@gmail.com",
  "subject": "GRB 130427A: NOT optical photometry and redshift",
  "submitter": "Dong Xu at DARK/NBI  <dong.dark@gmail.com>",
  "eventId": "GRB 130427A"
}