{
  "bibcode": "2014GCN.16977....1G",
  "body": "J. F. Graham (MPE Garching), D. A. Kann (TLS Tautenburg), P. Schady, and\nJ. Greiner (both MPE Garching) report on behalf of the GROND team:\n\nWe observed the field of GRB 141028A (Fermi trigger 436186489; LAT\ndetection: Bissaldi et al., GCN #16969; GBM Detection: Roberts; GCN\n#16971) 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 23:57 UT on October 28th, approximately 13 hours\nafter the GRB trigger. They were performed at an airmass of 1.2 and seeing\nof 1\".4.\n\nAt the position of the MASTER candidate afterglow (Gorbovskoy, GCN #16972)\nwe detect a bright source at\n\nRA (J2000.0) = 322.60226 = 21:30:24.54\nDEC (J2000.0) = -0.231314 = -00:13:52.7\n\nwith an error of 0\".5.\n\nBased on images with an exposure time of 1500 s in the optical and 1200 s\nin the NIR, centered at 0.55305 days after the trigger, we estimate\npreliminary magnitudes and limits (all in AB system) for this source of:\n\ng' = 20.76 +/- 0.02 mag\nr' = 19.93 +/- 0.01 mag\ni' = 19.70 +/- 0.02 mag\nz' = 19.49 +/- 0.02 mag\nJ = 19.24 +/- 0.11 mag\nH = 18.94 +/- 0.08 mag\nK > 18.3 mag\n\nCompared to the MASTER detection, the source has faded significantly. We\nalso detect a fading by 0.1 +/- 0.03 mag over the time span of an hour.\nFurthermore, the SED is adequately described by a power-law of slope beta\n= 1.1, with a possible g'-band dropout, which may point to a redshift of\naround 3 (which would make this a luminous afterglow).\n\nAt the position of the XRT source reported in the GRB_COUNTERPART POSITION\nNOTICE (Source 3 at http://www.swift.ac.uk/xrt_products/TILED_GRB00030/),\nwe detect no source down to limiting magnitudes of:\n\ng' > 24.5 mag\nr' > 24.4 mag\ni' > 23.7 mag\nz' > 23.4 mag\nJ > 20.9 mag\nH > 20.6 mag\nK > 18.3 mag\n\nWe therefore deem it likely the MASTER source represents the afterglow of\nGRB 141028A.\n\nGiven magnitudes are calibrated against SDSS field stars (g'r'i'z')\nand 2MASS field stars (JHK) and are not corrected for the expected\nGalactic foreground extinction corresponding to a reddening of E_(B-\nV) = 0.05 mag in the direction of the burst (Schlegel et al. 1998).",
  "circularId": 16977,
  "createdOn": 1414548183000,
  "email": "kann@tls-tautenburg.de",
  "subject": "GRB 141028A: GROND Afterglow confirmation (MASTER source)",
  "submitter": "Alexander Kann at TLS Tautenburg  <kann@tls-tautenburg.de>",
  "eventId": "GRB 141028A"
}