{
  "bibcode": "2007GCN..6664....1C",
  "body": "S. B. Cenko, A. Rau (Caltech), E. Berger (Carnegie/Princeton), P. A. Price\n(IfA), and A. Cucchiara (Penn State) report on behalf of a larger\ncollaboration:\n\nWe have imaged the field of GRB070724 (Ziaeepour et al., GCN 6654) on\nthe night of 2007 July 24 UT with the automated Palomar 60-inch telescope\n(beginning approximately 2.5 minutes after the burst) and the Gemini\nMulti-Object Spectrograph (GMOS) and Near-Infrared Imager (NIRI) mounted\non the 10-m Gemini North Telescope (beginning approximately 2 hours after\nthe burst).\n\nThe nearby galaxy first mentioned by Bloom (GCN 6658) shows no sign of\nvariability, either from our P60 to our GMOS imaging (remaining at a\nconstant magnitude of i' ~ 20.3), or within our Gemini imaging (verified\nwith psf-matched digital image subtraction).\n\nIn addition the aforementioned galaxy, we find a faint source on the\noutskirts of the revised XRT error circle (Page and Ziaeepour, GCN 6659)\nat coordinates (J2000.0):\n\n   RA: 01:51:14.05\n   Dec: -18:35:42.1\n\nwith an estimated astrometric uncertainty of approximately 0.3\" in each\ncoordinate.  The object is only visible in our Gemini/GMOS i' imaging of\nthe field, with a magnitude of i' ~ 24.6 (using GMOS zeropoints from the\nGemini webpage).  This object is not present in our earlier P60 imaging of\nthe field; however it is well below our detection threshold (see below).\nAs our only two Gemini/GMOS i' images were taken back-to-back, we have no\ninformation on the variability of this source at the current time.\n\nNo other object is detected in the revised XRT error circle in any other\nfilter.  Our limiting magnitudes, calculated with respect to the USNO-B\ncatalog (P60) or using zeropoints from the Gemini website (GMOS and NIRI),\nare quoted below:\n\nInstrument\tFilter\tUT (July 24)\tdt (hr)\tExposure (s)\tMagnitude\n---------------------------------------------------------------------------\nP60\t\ti'\t11:13\t\t0.32\t3x60 + 3x120\t> 21.5\nGMOS\t\ti'\t13:17\t\t2.38\t2x180\t\t> 24.5\nNIRI\t\tKs\t13:44\t\t2.83\t15x60\t\t> 20.0\nNIRI\t\tJ\t14:02\t\t3.13\t15x60\t\t> 22.0\nNIRI\t\tH\t14:19\t\t3.42\t15x60\t\t> 21.0\nNIRI\t\tKs\t14:36\t\t3.70\t15x60\t\t> 20.0",
  "circularId": 6664,
  "createdOn": 1185348520000,
  "email": "cenko@srl.caltech.edu",
  "subject": "GRB 070724: P60 and Gemini Observations",
  "submitter": "S. Bradley Cenko at Caltech  <cenko@srl.caltech.edu>",
  "eventId": "GRB 070724"
}