{
  "bibcode": "2015GCN.17729....1V",
  "body": "K. Varela, F. Knust, J. Bodensteiner and J. Greiner (all MPE Garching)\nreport on behalf of the GROND team:\n\nWe observed the field of GRB 150423A (Swift trigger 638808; Pagani et al.,\nGCN #17728) 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 06:32 UT on 2015-04-23, 4 min after the GRB\ntrigger. They were performed at an average seeing of 0\".8 and at an\naverage airmass of 1.5.\n\nWe detect a faint source within the 2.2\" XRT error circle, at position\n\nRA (2000.0) = 14h 46m 18.9s\nDecl (2000.0) = +12d 17' 00\"\n\nwith an error of 0.5\", about 1\" away from the XRT centroid position.\n\nBased on 7.7 min of total exposure time in g'r'i'z' and 8.0 min in JHK, \ncentered 24 min after the GRB, we estimate the following preliminary\nmagnitudes (all in AB system):\n\ng' = 23.2 +/- 0.2 mag,\nr' = 23.1 +/- 0.2 mag,\ni' = 22.5 +/- 0.2 mag,\nz' = 22.0 +/- 0.2 mag,\nJ  = 19.3 +/- 0.4 mag,\nH  > 18.4  mag, and\nK  > 17.5 mag.\n\nNo statement can be made about fading at this stage. Since there is a\nfaint source also in the SDSS, this might be the host galaxy rather than\nthe afterglow.\n\nGiven magnitudes are calibrated against SDSS (g'r'i'z') as well as 2MASS \nfield stars and are not corrected for the expected Galactic foreground \nextinction corresponding to a reddening of E_(B-V)=0.03 mag in the \ndirection of the burst (Schlegel et al. 1998).",
  "circularId": 17729,
  "createdOn": 1429774554000,
  "email": "jcg@mpe.mpg.de",
  "subject": "GRB 150423A: GROND observation",
  "submitter": "Jochen Greiner at MPI  <jcg@mpe.mpg.de>",
  "eventId": "GRB 150423A"
}