{
  "bibcode": "2009GCN..9262....1G",
  "body": "C. Guidorzi (Univ. Ferrara), R. Margutti (Univ. Bicocca & INAF-OAB),\nJ. Mao (INAF-OAB), and J. R. Cummings (NASA/UMBC) report on behalf of\nthe Swift-XRT team:\n\nWe have analysed the first two orbits of Swift-XRT data obtained for\nGRB 090426 (Cummings et al. GCN Circ. 9254), covering 3.0 ks of\nPhoton Counting (PC) mode data, between 88 s and 13.8 ks after the trigger.\nThe UVOT-enhanced XRT position was given by Osborne et al. in GCN Circ. \n9259.\n\nThe light-curve can be modelled by a simple power-law, with\na decaying index of 0.91 +/- 0.06 (chisq/dof=27.1/25).\n\nThe spectrum extracted from PC data in the time interval from 88 s\nto 5.6 ks can be modelled with an absorbed power-law, with a photon\nindex of 1.96 +/- 0.10 and a column density consistent with the Galactic\nvalue of 1.5e20 cm^-2 (Kalberla et al. 2005), with a 90% confidence upper\nlimit of 3.7e20 cm^-2. The observed (unabsorbed) 0.3 -10 keV flux over\nthis time interval is 1.1e-11 (1.2e-11) erg cm^-2 count^-1.\nUncertainties are given at 90% confidence.\n\nIf the light-curve continues to decay with alpha ~0.91, the count rate 24\nhours after the burst is estimated to be 3.9e-3 count s^-1, which\ncorresponds to an observed flux of 1.7e-13 erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00350479 .\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 9262,
  "createdOn": 1240777624000,
  "email": "guidorzi@fe.infn.it",
  "subject": "GRB 090426: Swift-XRT refined analysis",
  "submitter": "Cristiano Guidorzi at Ferrara U,Italy  <guidorzi@fe.infn.it>",
  "eventId": "GRB 090426"
}