{
  "bibcode": "2008GCN..7463....1P",
  "body": "C. Pagani and J. L. Racusin (PSU) report on behalf of the Swift-XRT team:\n\nThe Swift-XRT started observing GRB 080319A (trigger=306754, Pagani et al. GCN\n7426) at 05:54:59.4 UT, 557.4s after the trigger. The Swift slew to the burst\nwas delayed because of an Earth constraint and XRT observations were\ninterrupted by the Swift trigger on GRB 080319B. The current observations\nconsist of Photon Counting mode data from T+560s to T+1632s and from T+35ks to\nT+37ks.\n\nThe best XRT position is the UVOT-enhanced position from Beardmore et al. (GCN\n7448), consistent with the optical afterglow position reported by Cenko (GCN\n7429).\n\nThe 0.3-10 keV X-ray light curve starts at a count rate of ~1 counts/s and shows\na decline with a decay slope of 0.94 +/- 0.05.\n\nThe spectrum of the PC data from T+560s to T+1632s can be well fit by an\nabsorbed powerlaw with photon index 2.1 +/- 0.3 and column density of (1.0 +/-\n0.7)e21 cm^-2, in excess of the Galactic column density of 1.45e20 cm^-2 in\nthis direction. The average observed 0.3-10keV flux is 1.6e-11 erg cm^-2 s^-1,\nwhich corresponds to an unabsorbed flux of 2.1e-11 erg cm^-2 s^-1.  The counts\nto observed flux conversion factor at the time of this spectrum is 3.7e-11 erg\ncm^-2 count^-1.\n\nIf the underlying powerlaw decay continues as is, we predict an XRT count rate\nof 0.008 counts/s at T+24hr, which corresponds to an observed 0.3-10keV flux of\n2.9e-13 erg cm^-2 s^-1.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 7463,
  "createdOn": 1205964449000,
  "email": "pagani@astro.psu.edu",
  "subject": "GRB 080319A: Swift-XRT Team Refined Analysis",
  "submitter": "Claudio Pagani at PSU/Swift-XRT  <pagani@astro.psu.edu>",
  "eventId": "GRB 080319A"
}