{
  "bibcode": "2009GCN..9862....1O",
  "body": "F. Olivares, T. Kruehler and J. Greiner (all MPE Garching) report on behalf \nof the GROND team:\n\nWe observed the field of GRB 090831C (Swift trigger #361489; Schady et al., \nGCN #9854) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, \nPASP 120, 405) mounted at the 2.2 m ESO/MPI telescope at LaSilla \nObservatory (Chile).\n\nObservations started at 08:07 UT on September 1st, 2009, 10.6 hr after the \nburst. At this time the position of the burst was becoming visible above \nthe pointing constraints of the telescope. Observations suffer from high \nairmass and large seeing of around 2\". In stacked images of 74 min total \nintegration time in griz and 60 min in JHK, we do not detect any object \nwithin the enhanced XRT error circle (Evans et al., GCN #9855), down to the \nfollowing limiting magnitudes (all in the AB system):\n\ng' > 23.5\nr' > 24.0\ni' > 23.3\nz' > 22.9\nJ > 21.4\nH > 21.1\nK > 20.0\n\nThese upper limits were derived using the GROND zeropoints and 2MASS field \nstars as reference and are not corrected for significant Galactic \nforeground extinction corresponding to a reddening of E(B-V)=0.38 mag \n(Schlegel et al., 1998).",
  "circularId": 9862,
  "createdOn": 1251830716000,
  "email": "kruehler@mpe.mpg.de",
  "subject": "GRB 090831C: GROND upper limits",
  "submitter": "Thomas Kruehler at MPE/MPI  <kruehler@mpe.mpg.de>",
  "eventId": "GRB 090831C"
}