{
  "bibcode": "2011GCN.12757....1N",
  "body": "A. Nicuesa Guelbenzu, S. Klose (both TLS Tautenburg), and J. Greiner (MPE \nGarching) report on behalf of the GROND team:\n\nWe observed the field of GRB 111228A (Ukwatta et al., GCN 12737) \nsimultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, \n405) mounted at the 2.2-m MPG/ESO telescope on La Silla.\n\nObservations started as soon the object was visible over La Silla, at \n04:46 UT on December 29, about 13 hr after the burst. We detect the \nafterglow (Ukwatta et al., GCN 12737; Xin et al., GCN 12738) in all bands. \nAt a mean time of December 29, 05:35 UT, in an 8min exposure, we measure \nthe following preliminary magnitudes (AB system):\n\n    g' = 20.17  +/- 0.01,\n    r' = 19.84  +/- 0.01,\n    i' = 19.67  +/- 0.02,\n    z' = 19.50  +/- 0.03,\n    J  = 19.29  +/- 0.07,\n    H  = 18.93  +/- 0.08.\n\nThe SED is best fit with a spectral slope of 0.90 +/- 0.05, with no \nevidence for additional extinction.\n\nOptical data are calibrated against SDSS and NIR data against 2MASS field \nstars. Observations are continuing.",
  "circularId": 12757,
  "createdOn": 1325145333000,
  "email": "klose@tls-tautenburg.de",
  "subject": "GRB 111228A: GROND observations",
  "submitter": "Sylvio Klose at TLS Tautenburg  <klose@tls-tautenburg.de>",
  "eventId": "GRB 111228A"
}