{
  "bibcode": "2008GCN..8260....1S",
  "body": "G. Stratta, M. Perri, B. Preger (ASDC) report on behalf of the\nSwift-XRT team:\n\nWe have analyzed the first two orbits of Swift XRT data of\nGRB 080916B (Stratta et al., GCN Circ. 8242), consisting of\n2.8 ks of Photon Counting data collected starting\nfrom 22.8 min after the burst.\n\nDuring the XRT observation, from T0+1.4 ks to T0+8.5 ks,\nthe source shows a fading behaviour from 0.08 cts/s\nto 0.02 cts/s. Assuming a power law model, the best fit decay index is\nalpha = 1.0 � 0.2. At this rate we predict a count rate\nlevel of 1.7 x 10-3 cts/s one day after the trigger.\n\nThe 0.3-10 keV extracted spectrum (2.8 ks of integration time)\nis consistent with an absorbed power law model.\nFixing the column density to the Galactic value\n(NH = 1.8 x 1020 cm-2 from Kalberla et al. 2007)\nthe best fit photon index is 2.0 � 0.5.\n\nThe observed 0.3-10.0 keV flux is (1.0+/-0.6) x 10-12 erg cm-2 s-1\nwhich corresponds to an unabsorbed flux of 1.1 x 10-12  erg cm-2 s-1.\nThe count to observed flux conversion factor is 6.6 x 10-11 erg cm-2\ncount-1.\n\nThis Circular is an official product of the Swift-XRT team.",
  "circularId": 8260,
  "createdOn": 1221664637000,
  "email": "perri@asdc.asi.it",
  "subject": "GRB 080916B: Swift-XRT refined analysis",
  "submitter": "Matteo Perri at ISAC/ASDC  <perri@asdc.asi.it>",
  "eventId": "GRB 080916B"
}