{
  "bibcode": "2010GCN.10674....1S",
  "body": "M. C. Stroh, D. Grupe and E. A. Hoversten (PSU) report on behalf of the Swift-XRT team:\n\nWe have analysed 641 s of XRT data for GRB 100424A (Hoversten  et al.\nGCN Circ. 10667), from 126 s to 769 s after the  BAT trigger. The data\ncomprise 509 s in Windowed Timing (WT) mode with the remainder in\nPhoton Counting (PC) mode. The light curve can be modelled with a\nseries of power-law decays. The initial decay index is alpha=0.63\n(+/-0.14). At T+288 s the decay steepens to an alpha of 1.41 (+0.27,\n-0.19) before breaking again at T+526 s to a final decay with index\nalpha=2.8 (+0.9, -0.6).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.26 (+/-0.06). The\nbest-fitting absorption column is 1.62 (+0.22, -0.21) x 10^21 cm^-2,\nin excess of the Galactic value of 2.3 x 10^20 cm^-2 (Kalberla et al.\n2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion\nfactor deduced from this spectrum  is 5.8 x 10^-11 (6.5 x 10^-11) erg\ncm^-2 count^-1.\n\nIf the light curve continues to decay with a power-law decay index of\n2.8, the count rate at T+24 hours will be 5.1 x 10^-6 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.0 x\n10^-16 (3.3 x 10^-16) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00420367.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 10674,
  "createdOn": 1272168816000,
  "email": "stroh@astroh.org",
  "subject": "GRB 100424A: Swift-XRT refined analysis",
  "submitter": "Michael Stroh at PSU/Swift  <stroh@astroh.org>",
  "eventId": "GRB 100424A"
}