{
  "bibcode": "2012GCN.14049....1K",
  "body": "T. Kruehler (DARK/NBI), A. Nicuesa Guelbenzu (TLS Tautenburg) \nand J. Greiner (MPE Garching) report on behalf of the GROND team:\n\nWe observed the field of the Swift GRB 121209A (Maselli et al., GCN 14045)\nsimultaneously in g'r'i'z'JHKs with GROND (Greiner et al. 2008, PASP 120, 405)\nmounted at the 2.2m MPG/ESO telescope at La Silla Observatory (Chile).\n\nObservations started on December 10, 2012, 00:24 UT which is roughly 2.4 hr \nafter the trigger. Within the UVOT-enhanced XRT position (see link in Maselli et al.,\nGCN 14045), we detect a faint source in the stack of all g'r'i'z' data at:\n\nRA (J2000) = 21:47:08.96\nDec (J2000) = -08:14:06.3\n\nwith an estimated uncertainty of 0.5\" in each coordinate.\n\nForcing photometry on this position, we estimate preliminary AB magnitudes and \nupper limits in the individual filters of:\n\ng' > 24.0 mag\nr' = 23.9 +- 0.3 mag\ni' = 23.6 +- 0.4 mag\nz' = 23.2 +- 0.3 mag\nJ  > 21.5 mag\nH  > 21.0 mag\nKs > 19.5 mag\n\nThese magnitudes and upper limits are based on images with a mid-time \nof 00:59 UT and an effective integration time of 26.4 min in griz and \n24.0 min in the JHKs filters. They are calibrated against SDSS and 2MASS field stars \nand have not been corrected for the expected Galactic foreground extinction \ncorresponding to a reddening of  E(B-V) = 0.05 mag (Schlegel et al. 1998). \nNo statement about variability can be made at this point.",
  "circularId": 14049,
  "createdOn": 1355125077000,
  "email": "tom@dark-cosmology.dk",
  "subject": "GRB 121209A: GROND optical afterglow candidate",
  "submitter": "Thomas Kruehler at Dark Cosmology Center  <tom@dark-cosmology.dk>",
  "eventId": "GRB 121209A"
}