{
  "bibcode": "2010GCN.10304....1F",
  "body": "R. Filgas (MPE Garching), S. Klose (TLS Tautenburg), and J. Greiner (MPE \nGarching), report on behalf of the GROND team:\n\nGROND (Greiner et al. 2008, PASP 120, 405), the 7-channel imager mounted \nat the 2.2m ESO/MPI telescope at La Silla Observatory (Chile), started \nfollow-up NIR observations of GRB 091231 (Markwardt et al. 2009, GCN \n10301) on Jan 1, at 9:04 UT (about 15 hrs after the burst, shortly before \nsun rise).\n\nWe could not detect the afterglow candidate reported by Holland et al. \n(2009; GCN 10303). Based on a 4 min exposure, we estimate the following \npreliminary upper limits (in the Vega system):\n\nJ  > 16.7\nH  > 16.3\nK  > 15.2\n\nusing GROND zeropoints and the 2MASS catalog.\n\nDue to visibility constraints of the field from La Silla, no earlier \nobservations were possible.",
  "circularId": 10304,
  "createdOn": 1262342138000,
  "email": "klose@tls-tautenburg.de",
  "subject": "GRB 091231: GROND NIR observations",
  "submitter": "Sylvio Klose at TLS Tautenburg  <klose@tls-tautenburg.de>",
  "eventId": "GRB 091231"
}