{
  "bibcode": "2014GCN.16996....1T",
  "body": "M. Tanga, C. Delvaux (both MPE Garching), D. A. Kann (TLS Tautenburg), P.\nSchady and J. Greiner (both MPE Garching) report on behalf of the GROND\nteam:\n\nWe observed the field of GRB 141031A (Swift trigger 617110; Gompertz et\nal., GCN #16995) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.\n2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at the ESO La\nSilla Observatory (Chile).\n\nObservations started at 07:46 UT on 31 October 2014, 0.45 hrs after the\nGRB trigger. They were performed at an average seeing of 1.3\" and at an\naverage airmass of 1.33.\n\nWe found one single point source at the NW edge of the 2.1\" Swift-XRT\nerror circle reported by Gompertz et al. (GCN #16995) at\n\nRA (J2000.0) = 08h 34m 25.75s\n\nDEC (J2000.0) = -59d 10' 05.0\"\n\nwith an uncertainty of 0.3\" in each coordinate.\n\nBased on the first 8.8 min of total exposures in g'r'i'z' and 8.0 min in\nJHK, we estimate preliminary magnitudes (all in AB system) of\n\ng' = 22.7 +/- 0.1 mag,\nr' = 21.7 +/- 0.1 mag,\ni' = 21.5 +/- 0.1 mag,\nz' = 21.5 +/- 0.1 mag,\nJ > 20.9 mag,\nH > 20.3 mag, and\nK > 18.7 mag.\n\nAt the moment we cannot confirm if the source is fading.\n\nGiven magnitudes are calibrated against GROND zeropoints as well as 2MASS\nfield stars and are not corrected for the expected Galactic foreground\nextinction corresponding to a reddening of E_(B-V)=0.17 mag in the\ndirection of the burst (Schlegel et al. 1998).",
  "circularId": 16996,
  "createdOn": 1414755331000,
  "email": "delvaux@mpe.mpg.de",
  "subject": "GRB 141031A: GROND detection of a possible optical afterglow candidate",
  "submitter": "Corentin Delvaux at MPE  <delvaux@mpe.mpg.de>",
  "eventId": "GRB 141031A"
}