{
  "bibcode": "2016GCN.18921....1D",
  "body": "C. Delvaux (MPE Garching), S. Schmidl (TLS Tautenburg), and J. Greiner\n(MPE Garching) report on behalf of the GROND team:\n\nWe observed the field of GRB 160121A (Swift trigger 671231; Hagen et al.,\nGCN #18912) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,\nPASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla\nObservatory (Chile).\n\nObservations started at 04:09 UT on 22-01-2016, 14.3hrs after the GRB\ntrigger. They were performed at an average seeing of 0.9\" and at an\naverage airmass of 1.0.\n\nWe clearly detect the afterglow at the position reported by Oates et al.\n(GCN#18917) and Mazaeva et al. (GCN#18920).\n\nBased on the first 72 min of total exposures in g'r'i'z' and 60 min in\nJHK, at a midtime of 04:49 UT, we estimate preliminary magnitudes and\nupper limits (all in AB system) of\n\ng' = 22.6 +/- 0.1 mag\nr' = 21.2 +/- 0.1 mag,\ni' = 21.1 +/- 0.1 mag,\nz' = 21.0 +/- 0.1 mag,\nJ =  19.6 +/- 0.1 mag,\nH =  19.3 +/- 0.1 mag,\nK > 19.1 mag.\n\nThe given magnitudes and limits are derived based on calibrating the\nimages against GROND zeropoints and 2MASS field stars and are not\ncorrected for the Galactic foreground extinction corresponding to a\nreddening of E_(B-V)= 0.53 in the direction of the burst (Schlafly and\nFinkbeiner 2011).",
  "circularId": 18921,
  "createdOn": 1453451802000,
  "email": "delvaux@mpe.mpg.de",
  "subject": "GRB 160121A: GROND Afterglow observations",
  "submitter": "Corentin Delvaux at MPE  <delvaux@mpe.mpg.de>",
  "eventId": "GRB 160121A"
}