{
  "bibcode": "2012GCN.14091....1E",
  "body": "J. Elliott (MPE Garching), S. Schmidl (TLS Tautenburg), and J.Greiner (MPE\nGarching) report on behalf of the GROND team:\n\nWe observed the field of GRB 121217A (Swift trigger 542441; Siegel et al.,\nGCN 14089) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,\nPASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at La Silla\nObservatory (Chile).\n\nObservations started on December 17, 2012, at 07:21 UT, 210 s after the\nGRB trigger. They were performed at an average seeing of 1.6\" and at an\naverage airmass of 1.2.\n\nWe found a fading point source at the border of the enhanced XRT error\ncircle given in Evans et al. (GCN 14090)\n\nRA (J2000.0) = 10:14:50.407\nDEC (J2000.0) = -62:21:03.53\n\nwith an uncertainty of 0.5\" in each coordinate.\n\nBased on a total exposure time of 456 s in g'r'i'z' and 480 s in JHK,\nat a midtime of 1882 s after the burst, we estimate preliminary\nAB magnitudes of\n\ng' = 20.3 +/- 0.1,\nr' = 19.3 +/- 0.1,\ni' = 18.9 +/- 0.1,\nz' = 18.6 +/- 0.1,\nJ  = 18.1 +/- 0.1,\nH  = 17.7 +/- 0.1,\nK  = 17.4 +/- 0.1.\n\nIn the r' band the source faded with a decay slope of 0.7 +/- 0.1\nbetween 2000 s and  4200 s after the trigger. The SED can be fit\nwith a power-law with a slope of beta = 0.8 +/- 0.1.\n\nGiven magnitudes are calibrated against GROND zeropoints as well as 2MASS\nfield stars and are not corrected for the Galactic foreground extinction\ncorresponding to a reddening of E(B-V)= 0.38 mag in the direction of the\nburst (Schlegel et al. 1998).\n\nThe extinction-corrected SED suggests a photo-z of 3.0 +/- 0.2. We\ncaution, however, that the high Galactic extinction along the line of\nsight might affect this result.",
  "circularId": 14091,
  "createdOn": 1355751176000,
  "email": "schmidl@tls-tautenburg.de",
  "subject": "GRB 121217A: GROND Detection of the Afterglow",
  "submitter": "Sebastian Schmidl at TLS Tautenburg  <schmidl@tls-tautenburg.de>",
  "eventId": "GRB 121217A"
}