{
  "bibcode": "2018GCN.22819....1S",
  "body": "Tassilo Schweyer and Patricia Schady (MPE Garching) report:\n\nWe observed the field of GRB 180620B (Swift trigger 843211; Evans et al.,\nGCN #22807) 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 05:06 UT on 2018-06-21, 13.3 hours after the GRB\ntrigger. They were performed at an average seeing of 1.6\" and at an\naverage airmass of 1.5.\n\nWe found a single, bright point source within the 1.4\" Swift-XRT enhanced\nerror circle reported by Beardmore et al. (GCN #22814) at\n\nRA (J2000.0) = 23:50:05.088\nDec (J2000.0) = -57:57:43.88\n\nwith an uncertainty of 0.14\" in each coordinate.\n\nBased on a total exposure time of around 30mins we estimate the following\nAB magnitudes:\n\ng' = 21.3 +/- 0.1 mag\nr' = 20.8 +/- 0.1 mag\ni' = 20.4 +/- 0.1 mag\nz' = 20.3 +/- 0.1 mag\nJ = 19.7 +/- 0.1 mag\nH = 19.6 +/- 0.2 mag\nK = 19.1 +/- 0.4 mag\n\nGiven magnitudes are calibrated against GROND zeropoints as well as 2MASS\nfield stars and are not corrected for the expected Galactic foreground\nextinction corresponding to a reddening of E_(B-V)=0.01 in the direction\nof the burst (Schlafly & Finkbeiner 2011).\n\nWe thank Markus Rabus for the excellent support from La Silla.",
  "circularId": 22819,
  "createdOn": 1529579936000,
  "email": "pschady@mpe.mpg.de",
  "subject": "GROND observations of GRB 180620B",
  "submitter": "Patricia Schady at MPE/Swift  <pschady@mpe.mpg.de>",
  "eventId": "GRB 180620B"
}