{
  "bibcode": "2007GCN..6737....1E",
  "body": "P.A. Evans, K.L. Page (U. Leicester) and F. E. Marshall (NASA/GSFC) report on\nbehalf of the Swift-XRT team:\n\nWe have analysed the first 11 ks of Swift XRT data for GRB 070809\n(Marshall et al. GCN Circ 6728), all of which is in Photon Counting (PC)\nmode. We find a refined XRT position of RA, Dec = 203.7699, -22.1416\ndegrees, which is equivalent to:\n\nRA (J2000) = 13h 35m 4.78s\nDec(J2000) = -22d 08' 29.8\"\n\nwith an estimated uncertainty of 3.5 arcsec (radius, 90% containment\nincluding systematics). This is 81.9\" from the refined BAT position\n(Krimm et al. GCN Circ 6732) and 4.2\" from the XRT position reported in\nGCN Circ 6728.\n\nThe XRT light curve shows fading behaviour which is well fitted by a\npower-law with two breaks. The initial decay followed a slope of\nalpha=2.3 (+0.7/-1.1), and then broke at ~T0+200 s to a shallow decay\nwith alpha=0.28 (+/-0.13). The shallow phase ended at approximately\nT0+10000 s and the current decay follows a slope of alpha=1.35\n(+0.80/-0.72).\n\nThe PC mode spectrum from T0+85-25000 s is well fitted by an absorbed\npower-law with a column density of 6.7e20 (+7.0e20/-5.3e20) cm^-2,\nconsistent with the Galactic value of 6.40e20 cm^-2 (Kalberla et al.\n2005). The spectral slope was gamma=1.49 (+0.25/-0.22), consistent with\nthe BAT value (GCN Circ 6732). The observed (unabsorbed) 0.3-10 keV flux\nis 1.64e-12 (1.79e-12) erg cm^-2 s^-1.\n\nIf the source continues to decay with alpha=1.35, we predict a count\nrate of 1.7e-3 counts s^-1 at T0+24 hours, which corresponds to an\nobserved  (unabsorbed) flux of 1.09e-13 (1.20e-13) erg cm^2 s^-1.\n\nThis circular is an official product of the Swift/XRT team.",
  "circularId": 6737,
  "createdOn": 1186735466000,
  "email": "pae9@star.le.ac.uk",
  "subject": "GRB 070809: Swift-XRT refined analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@star.le.ac.uk>",
  "eventId": "GRB 070809"
}