{
  "bibcode": "2014GCN.17041....1G",
  "body": "J. Graham (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 141109A (Swift trigger 618024; P. D'Avanzo\net al., GCN 17037) simultaneously in g'r'i'z'JHK with GROND (Greiner et\nal. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La\nSilla Observatory (Chile).\n\nObservations started at 06:51 UT on November 09, 2014, approximately 1\nhour after the GRB trigger. They were performed at an average seeing of\n1.7\" and at an average airmass of 1.6.\n\nWe detect the optical/NIR aftergow reported by Covino et al. (GCN 17039)\nand Xu et al. (GCN 17040).\n\nBased on total exposures of 25.0 minutes in g'r'i'z' and 20.0 minutes in\nJHK, at a midtime of 2.3 hrs after the burst, we measure the following\npreliminary magnitudes (AB magnitude system):\n\ng' = 20.7 +/- 0.1 mag,\nr' = 19.7 +/- 0.1 mag,\ni' = 19.4 +/- 0.1 mag,\nz' = 19.2 +/- 0.1 mag,\nJ = 19.0 +/- 0.1 mag,\nH = 18.8 +/- 0.1 mag, and\nK = 18.5 +/- 0.1 mag.\n\nThe magnitudes are calibrated against SDSS and 2MASS field stars and are\nnot corrected for the Galactic foreground extinction corresponding to a\nreddening of E_(B-V)= 0.04 in the direction of the burst (Schlegel et al.\n1998).",
  "circularId": 17041,
  "createdOn": 1415534654000,
  "email": "schmidl@tls-tautenburg.de",
  "subject": "GRB 141109A: GROND afterglow observation",
  "submitter": "Sebastian Schmidl at TLS Tautenburg  <schmidl@tls-tautenburg.de>",
  "eventId": "GRB 141109A"
}