{
  "bibcode": "2009GCN.10286....1F",
  "body": "R. Filgas, P. Afonso (both MPE Garching), S. Klose (TLS Tautenburg), and \nJ. Greiner (MPE Garching), 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 observations of GRB 091221 (Krimm et al. 2009, GCN 10283) on Dec \n22, at 01:27 UT (4.5 hrs after the burst).\n\nFor the suggested GRB afterglow (Zheng et al. 2009, GCN 10284; Holland et \nal. 2009, GCN 10285), based on a first 8 min exposure, we estimate the \nfollowing preliminary magnitudes (in the AB system):\n\ng' = 22.90 +/- 0.30\nr' = 22.27 +/- 0.30\ni' = 21.95 +/- 0.30\nz' = 22.20 +/- 0.30\nJ  = 20.16 +/- 0.20\nH  > 19.9\nK  > 19.1\n\nusing GROND zeropoints and 2MASS catalog (airmass 1.8). Observations are \nongoing.\n\nTaking into account a Galactic reddening of E(B-V)=0.22 mag (Holland et \nal. 2009, GCN 10285), we estimate a photometric redshift of z<3.5. At \npresent we cannot decide if the z'-band magnitude is indicating to a \nbroad-band absorption feature or if we underestimate the magnitude error\nin this band (where the source is very faint).",
  "circularId": 10286,
  "createdOn": 1261452001000,
  "email": "klose@tls-tautenburg.de",
  "subject": "GRB 091221, GROND observations",
  "submitter": "Sylvio Klose at TLS Tautenburg  <klose@tls-tautenburg.de>",
  "eventId": "GRB 091221"
}