{
  "bibcode": "2008GCN..8530....1V",
  "body": "L. Vetere, E. Hoversten (PSU) report on behalf of the Swift-XRT team.\n\nThe Swift-XRT started observing the field of GRB 081118 (trigger=334877,\nHoversten et al., GCN 8525) at 14:59:10.0 UT, 153.3 s after the BAT  \ntrigger.\nThe XRT observed the GRB in Windowed Timing (WT) mode until 216 s\nafter the trigger and Photon Counting (PC) mode thereafter.\n\nThe X-ray light curve from the first three orbits can be modelled with  \na broken\npowerlaw with an initial rapid decay (slope of 4.8+/-1.0), a break  \ntime of 580 s,\nfollowed by a shallower decay (slope of 0.6+/-0.3).\n\nThe spectrum of the WT data can be well fit by an absorbed powerlaw  \nwith a\nphoton index of 2.6 +/- 0.3 and an absorbing equivalent hydrogen column\ndensity consistent with the Galactic one in the GRB direction (3.7e20  \ncm^-2;\nKalberla et al.  2005). The observed (unabsorbed) 0.3-10 keV flux is  \n1.79\n(2.28) x 10^-10 erg cm^-2 s^-1.\n\nThe PC spectrum (T+250 s to T+19 ks) is best fit with a photon index of\n2.5 +/- 0.3 and an absorbing equivalent hydrogen column density  \nconsistent\n  with the Galactic one in the GRB direction (3.7e20 cm^-2; Kalberla  \net al.  2005).\nThe observed (unabsorbed) 0.3-10 keV flux over this interval is 7.6  \n(9.4) x\n10^-13 erg cm^-2 s^-1.\n\nAssuming the X-ray emission from the burst continues to decline at the\nsame rate we predict an XRT count rate of 0.002 count s^-1 at T+24 hour,\nor an observed 0.3-10 keV X-ray flux of 5.2 x 10^-14 erg cm^-2 s^-1.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 8530,
  "createdOn": 1227067796000,
  "email": "vetere@astro.psu.edu",
  "subject": "GRB 081118: Swift-XRT refined analysis",
  "submitter": "Loredana Vetere at PSU  <vetere@astro.psu.edu>",
  "eventId": "GRB 081118"
}