{
  "bibcode": "2018GCN.22777....1S",
  "body": "P. Schady, T. Schweyer, T.-W. Chen (all MPE Garching) and J. Bolmer (ESO\nSantiago) report:\n\nWe observed the field of GRB 180613A (Swift trigger 840853; Tohuvavohu et\nal., GCN #22769) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.\n2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla\nObservatory (Chile).\n\nObservations started at 23:30 UT on 2018-06-13, 7.9 hrs after the GRB\ntrigger. They were performed at an average seeing of 1.5\" and at an\naverage airmass of 1.1.\n\nWe do not detect the HAWKI source reported by Thoene et al. (GCN #2275).\nHowever, we note that the larger 4.9 arcsec uncertainty on the enhanced\nXRT position (Beardmore et al., GCN #22773) now includes two, brighter\nsources that are below the sensitivity of the DSS images.\n\nSource #1 lies at the SW edge of the enhanced XRT 90% error circle, at\n\nRA = 14:06:05.24\nDec = -43:04:21.6\n\nwith a preliminary magnitude r' = 23.1 +/- 0.1 mag.\n\nSource #2 lies at the NW edge of the enhanced XRT error circle, at\n\nRA = 14:06:05.24\nDec = -43:04:21.6\n\nwith r' = 22.9 +/- 0.1 mag. The above positions have an accuracy of 0.1\"\nin both directions.\n\nOur g' band photometry is strongly affected by a nearby 5.6 mag star\nlocated SW of the GRB position, but source #1 is detected in all other\nGROND bands. Source #2 is detected in r', i' and z'. Our observations at\nthe position of the XRT afterglow have preliminary 3 sigma upper limits of\n\nr' > 23.7 mag\ni' > 22.8 mag\nz' > 22.7 mag\nJ > 21.5 mag\nH > 21.0 mag\nK > 20.4 mag\n\nAll quoted magnitudes are in the AB system and are calibrated against\nGROND zeropoints and 2MASS field stars. They are not corrected for the\nGalactic foreground extinction corresponding to a reddening of E_(B-V)=\n0.08 in the direction of the burst (Schlafly & Finkbeiner 2011).",
  "circularId": 22777,
  "createdOn": 1528976527000,
  "email": "pschady@mpe.mpg.de",
  "subject": "GRB 180613A GROND observations",
  "submitter": "Patricia Schady at MPE/Swift  <pschady@mpe.mpg.de>",
  "eventId": "GRB 180613A"
}