{
  "bibcode": "2009GCN..9961....1V",
  "body": "L. Vetere (PSU) reports on behalf of the Swift-XRT team:\n\nWe have analyzed the first 21.8 ks of Swift-XRT data of FERMI\nGRB090926A (Bissaldi et al., GCN Circ. 9933). The UVOT-enhanced XRT\nposition for this burst was given in GCN Circ.9936 (Vetere et al.).\n\nThe data are entirely in Photon Counting (PC) mode from T+46.7 ks\nto T+203 ks. The light curve shows a decaying behaviour with some\nflaring activity. It is best fitted by a power-law with decay index\n1.29+/-0.2. Assuming the X-ray emission from the burst continues\nto decline at the present rate, the predicted count rate at T+3d\nis 0.009 cts/s.\n\nThe average spectrum is best fit by an absorbed power-law model\nwith a photon spectral index of 2.6 (+0.3,-0.2) and an absorption\ncolumn density of 1.0 (+0.5,-0.3)e21 cm-2 in excess of the Galactic\nvalue of 2.7e20 cm-2 (Kalberla et al. 2005). The counts-to-observed\n0.3-10 keV flux conversion factor deduced from this spectrum is\n3.5e-11 erg cm-2 count-1. The average observed (unabsorbed) fluxes\nare 1.3 (1.9)E-12 ergs cm-2 s-1. Errors are given at the 90%\nconfidence level.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 9961,
  "createdOn": 1254175192000,
  "email": "vetere@astro.psu.edu",
  "subject": "GRB090926A: Swift-XRT refined analysis",
  "submitter": "Loredana Vetere at PSU  <vetere@astro.psu.edu>",
  "eventId": "GRB 090926A"
}