{
  "bibcode": "2016GCN.18967....1K",
  "body": "F. Knust, J. Bolmer, J. Greiner (all MPE Garching), and D. A. Kann,  (TLS\nTautenburg) report on behalf of the GROND team:\n\nWe observed the field of GRB 160131A (Swift trigger 672236; Page et al.,\nGCN #18951) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,\nPASP 120, 405) mounted at the 2.2m MPG telescope at ESO La Silla\nObservatory (Chile).\n\nObservations started at  0:44 UT on 2016-02-01, 16 hrs after the GRB\ntrigger, and are continuing. They were performed at an average seeing of\n1.3\" and at an average airmass of 1.1.\n\nWe found a single point source within the 2.2\" Swift-XRT error circle\nreported by Goad et al. (GCN #18958), in agreement with the UVOT afterglow\n (Page et al., GCN #18951) at\n\nRA (J2000.0) = 05 h 12 m 40.32 s\nDec. (J2000.0) = -07d 02' 58.92\n\nwith an uncertainty of 0.5\" in each coordinate.\n\nBased on the first 4.40 min of total exposures in g'r'i'z' and 4.0 min in\nJHK, we estimate preliminary magnitudes (all in AB system) of\n\ng' = 18.7 +/- 0.05 mag,\nr' = 18.4 +/- 0.05 mag,\ni' = 18.3 +/- 0.05 mag,\nz' = 18.2 +/- 0.05 mag,\nJ  = 17.7 +/- 0.1 mag,\nH  = 17.6 +/- 0.1 mag, and\nK  = 17.1 +/- 0.1 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)=0.09 mag in the\ndirection of the burst (Schlafly & Finkbeiner 2011).",
  "circularId": 18967,
  "createdOn": 1454289614000,
  "email": "fknust@mpe.mpg.de",
  "subject": "GRB 160131A: GROND Detection of the Optical/NIR Afterglow",
  "submitter": "Fabian Knust at MPE/GROND  <fknust@mpe.mpg.de>",
  "eventId": "GRB 160131A"
}