{
  "bibcode": "2009GCN..9209....1C",
  "body": "A. Cucchiara (PSU), D. B. Fox (PSU), and E. Berger (Harvard) report:\n\n\"On April 23.33 UT we imaged the field of Swift GRB 090423 (Krimm et\nal., GCN 9198) with NIRI on the Gemini-North telescope.  We obtained\n9x60 sec exposures in Y,J,H.  In the coadded J and H images we clearly\nidentify the object noted by Tanvir et al. (GCN 9202) and it appears\npoint-like (see also Levan et al., GCN 9206). The object is not\ndetected in Y-band.\n\nWe derive the following magnitudes, calibrated using three 2MASS stars\nin the field:\n\nJ mag: 19.29 +- 0.07\nH mag: 17.71 +- 0.14\n\nThe resulting J-H color of 1.1 AB mag is very red, corresponding to a\nsteep spectral slope of beta=3.8.  Taken in conjunction with a flat\nH-K color (see GCN 9202), our non-detection in Y-band, and a red I-J\ncolor of 1.7 AB mag in comparison to P60 limits (GCN 9201), we suggest\nthat there is a likely break in the spectrum at about 1.2 microns,\nwith extinction an unlikely explanation due to the sharpness of the\nfeature and the shallow slope to redder wavelengths.  If this is due\nto Ly-alpha absorption, then the resulting redshift for GRB 090423 is\nz~9.\n\nFurther analysis is in progress and additional observations are\nplanned.\"",
  "circularId": 9209,
  "createdOn": 1240498950000,
  "email": "dfox@astro.psu.edu",
  "subject": "GRB 090423:  NIR photometry and evidence for spectral break",
  "submitter": "Derek Fox at PSU  <dfox@astro.psu.edu>",
  "eventId": "GRB 090423"
}