{
  "bibcode": "2013GCN.14866....1S",
  "body": "S. Schmidl, A. Rossi (both TLS Tautenburg), and J. Greiner (MPE\nGarching) report on behalf of the GROND team:\n\nWe observed the field of GRB 130609B (Swift trigger 557828; Krimm et\nal., GCN #14841) simultaneously in g'r'i'z'JHK with GROND (Greiner\net al. 2008, PASP 120, 405) mounted at the 2.2 m MPG/ESO telescope\n  at La Silla Observatory (Chile).\n\nObservations started at 09:30 UT on 11th June 2013, 35.9 hours after\nthe GRB trigger. They were performed at an average seeing of 1.6\"\nand at an average airmass of 2.2.\n\nWe detect a source at the position of the UVOT afterglow (Siegel\net al.; GCN #14857), and based on images taken at a mid-time of\n09:45 UT, with total exposures of 25 minutes in g'r'i'z' and 20\nminutes in JHK, we estimate preliminary magnitudes (all in AB) of\n\ng' = 22.2 +/- 0.1 mag,\nr' = 21.7 +/- 0.1 mag,\ni' = 21.1 +/- 0.2 mag,\nz' = 20.9 +/- 0.2 mag,\nJ = 20.6 +/- 0.3 mag,\nH = 19.8 +/- 0.4 mag, and\nK = 19.4 +/- 0.4 mag.\n\nThe source is brighter than what one could expect extrapolating\nthe early UVOT data (Siegel et al.; GCN #14857) and could be either\na plateau/flare, or due to the contribution of the host galaxy.\n\nGiven magnitudes are calibrated against GROND zeropoints as well as\n2MASS field stars and are not corrected for the expected Galactic\n  foreground extinction corresponding to a reddening of E_(B-V)=0.01 mag\nin the direction of the burst (Schlegel et al. 1998).",
  "circularId": 14866,
  "createdOn": 1370956602000,
  "email": "rossi@tls-tautenburg.de",
  "subject": "GRB 130609B: GROND observations",
  "submitter": "Andrea Rossi at TLS Tautenburg  <rossi@tls-tautenburg.de>",
  "eventId": "GRB 130609B"
}