{
  "bibcode": "2015GCN.18461....1K",
  "body": "F. Knust (MPE Garching), S. Klose (TLS Tautenburg), and J. Greiner \n(MPE Garching) report on behalf of the GROND team: \n\nWe observed the field of GRB 151023A (Swift trigger 661253; D'Avanzo\net al., GCN #18450) simultaneously in g'r'i'z'JHK with GROND (Greiner\net al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO\nLa Silla Observatory (Chile). \nObservations started at 23:52 UT on Oct. 23rd 2015, 10 hrs after the\nGRB trigger, and are continuing. They were performed at an average\nseeing of 1.6\" and at an average airmass of 1.6  \nWe found a single point source within the 2.3\" Swift-XRT error circle\nreported by Evans et al. (GCN #18459) at \n\nRA (J2000.0) = 18:03:56.244 \nDec. (J2000.0) = -08:18:57.42\n\nwith an uncertainty of 0.2\" in each coordinate. \nBased on the first 4.4 min of total exposures in g'r'i'z' and 4.0 min\nin JHK, we estimate preliminary magnitudes (all in AB system) of \n\ng'> 22.1 mag,\nr' = 20.2 +/- 0.1 mag,\ni' = 19.1 +/- 0.1 mag,\nz' =18.4 +/- 0.1 mag,\nJ = 17.6 +/- 0.2 mag,\nH = 17.0 +/- 0.1 mag, and\nK = 17.3 +/- 0.2 mag.\n\nGiven magnitudes are calibrated against GROND zeropoints as well as\n2MASS field stars and are not corrected for the expected Galactic\nforeground extinction corresponding to a reddening of E_(B-V)=1.38\nmag in the direction of the burst (Schlegel et al. 1998).         \t\t \t   \t\t  \n\n[GCN OPS NOTE(24oct15):  The suffix \"A\" was added to the Subject-line.]",
  "circularId": 18461,
  "createdOn": 1445649120000,
  "email": "fknust@mpe.mpg.de",
  "subject": "GRB 151023A",
  "submitter": "Fabian Knust at MPE/GROND  <fknust@mpe.mpg.de>",
  "eventId": "GRB 151023A"
}