{
  "bibcode": "2005GCN..3956....1F",
  "body": "D. B. Fox (PSU), C. Pagani (PSU/INAF-OAB), L. Angelini (GSFC),\nD. N. Burrows (PSU), J. P. Osborne (U. Leicester), and V. La Parola\n(INAF-IASF) report:\n\n\"We have analyzed the Swift/XRT observations of the BAT localization\nregion for the short-hard burst GRB 050906 (Parsons et al., GCN 3935).\n\nDuring the first orbit only, there is evidence for an excess of counts\nnear the position:\n\n     RA 03:31:15.6, Dec -14:36:37 (J2000)\n\nwhere we have corrected the XRT coordinates by roughly 6-arcsec from\nthe native astrometry using a bright star / X-ray source in the field.\nWithin a 20-pixel (47-arcsec) radius of this position, 6 photons are\ndetected where 0.9 photons are expected from the background,\nrepresenting a detection at 99.7%-confidence when considered over the\nfull XRT field of view.  If due to an astrophysical source, the\nsource's estimated count rate is 7.5 +/- 5.2 cts/ksec (90%-confidence)\nover the 798 seconds of observation, and the source positional\nuncertainty is 18 arcsec (90%-confidence radius).  Subsequent XRT\nobservations reveal no further excess count detections within this\nregion.  The source location is not coincident with either the VLA\nsource (Cameron & Frail, GCN 3933) or the bright galaxy (Levan &\nTanvir, GCN 3927; Parsons et al., GCN 3935) that have been identified\nin observations of this burst.\n\nWe note that: (1) The location of the excess is 13 arcsec outside the\n2.6-arcmin radius (90%-confidence) BAT localization region (Parsons et\nal., GCN 3935); (2) The temporal distribution of the counts during the\nfirst orbit is consistent with the temporal distribution of the\ndetector background counts (88%-confidence via two-sided K-S test);\n(3) The spatial distribution of the counts appears flat rather than\nPSF-like (unquantified); and (4) The source region lies within a\nregion of increased local background, towards the end of the first\norbit, due to emission from the bright Earth limb (two counts arrive\nduring the last 100 seconds; however, the event grades are distinct\nfrom those associated with the bright Earth limb).  Given these\ncaveats, we are not confident that the counts excess represents the\ndetection of an astrophysical source.  However, if it is due to a real\nsource, it is the most likely X-ray counterpart to GRB 050906.\"",
  "circularId": 3956,
  "createdOn": 1126289813000,
  "email": "dfox@astro.psu.edu",
  "subject": "GRB 050906: Possible X-ray Counterpart",
  "submitter": "Derek Fox at PSU  <dfox@astro.psu.edu>",
  "eventId": "GRB 050906"
}