{
  "bibcode": "2009GCN..9217....1P",
  "body": "D. A. Perley, S. B. Cenko, and J. S. Bloom (UC Berkeley) report on\nbehalf of GRAASP:\n\nWe initiated a series of 15 x 200 second exposures of the field of GRB\n090423 (Krimm et al, GCN 9198) in z-band using GMOS on Gemini-South\nstarting at 23:38 UT on 2009-04-23, 15.71 hours after the trigger.  No\nsource is visible in the XRT error circle (Evans et al., GCN 9205) or\nthe NIR position (Tanvir et al., GCN 9202) in the co-added image.  We\nestimate a limiting magnitude (3-sigma) of:\n\nz > 26.0 mag (t_mid = 16.25 hr)\n\nThis observation is nearly co-eval with the GROND photometry (Olivares\net al., GCN 9215) which detects the counterpart with a magnitude of J_AB\n= 21.6, implying a color of J-z > 4.4 (AB).  This, along with the\nnon-detection of a lower-redshift host galaxy candidate, the TNG\nspectrum (Thoene at al., GCN 9216), and the nearly flat JHK SED,\nconfirms the very high redshift (z > 7) of this event.\n\nWe thank Eleazar Carrasco and the Gemini observing staff for acquiring\nthese observations.",
  "circularId": 9217,
  "createdOn": 1240545112000,
  "email": "dperley@astro.berkeley.edu",
  "subject": "GRB 090423: Deep z-band upper limit and confirmation of photo-z",
  "submitter": "Daniel Perley at U.C. Berkeley  <dperley@astro.berkeley.edu>",
  "eventId": "GRB 090423"
}