{
  "bibcode": "2016GCN.19114....1D",
  "body": "C. Delvaux, T. Schweyer (both MPE Garching), D. A. Kann (TLS Tautenburg),\nand J. Greiner (MPE Garching) report on behalf of the GROND team:\n\nWe observed the field of GRB 160228A (Swift trigger 676595; Malesani et\nal., GCN #19107) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.\n2008, PASP 120, 405) mounted at the 2.2m MPG telescope at the ESO La Silla\nObservatory (Chile).\n\nObservations started at 00:02 UT on 2016-02-29, 6.4h after the GRB\ntrigger. They were performed at an average seeing of 1.2\" and at an\naverage airmass of 1.9.\n\nWe detect a single source at the edge of the Swift-XRT error circle\nreported by Beardmore et al. (GCN #19110) at\n\nRA (J2000.0) = 07h09m15.82s\nDec. (J2000.0) = +26d55'53.8\"\n\nwith an uncertainty of 0.2\" in each coordinate.\n\nBased on 132 min of exposure in g'r'i'z' and 110 min in JHK, at a mid-time\nof 01:46 UT, we derive the following preliminary magnitudes and upper\nlimits (in AB system):\n\ng' = 24.4 +/- 0.1 mag,\nr' = 24.4 +/- 0.1 mag,\ni' = 23.8 +/- 0.2 mag,\nz' = 24.1 +/- 0.3 mag,\nJ > 22.3 mag,\nH > 21.6 mag, and\nK > 19.4 mag.\n\nWe note the presence of a very close-by (separation < 2\") extended bluish\nobject, lying outside the Swift-XRT error circle, which could be the host\ngalaxy of the candidate. Another host could be a larger, brighter galaxy\nlying at the north of the Swift-XRT error circle (separation ~ 6.6\").\n\nWe found no evidence of fading of the candidate. Therefore, we cannot\naffirm the detected source is the optical afterglow.\n\nGiven detections and upper limits are calibrated against GROND zeropoints\nas well as 2MASS field stars. No correction for the expected Galactic\nforeground extinction corresponding to a reddening of E_(B-V)=0.056 mag in\nthe direction of the burst (Schlafly & Finkbeiner 2011) has been applied.",
  "circularId": 19114,
  "createdOn": 1456724860000,
  "email": "delvaux@mpe.mpg.de",
  "subject": "GRB 160228A: GROND Afterglow Candidate",
  "submitter": "Corentin Delvaux at MPE  <delvaux@mpe.mpg.de>",
  "eventId": "GRB 160228A"
}