{
  "bibcode": "2010GCN.11014....1E",
  "body": "P. A. Evans (U. Leicester) and J. K. Cannizzo (NASA/UMBC) report on\nbehalf of the Swift-XRT team:\n\nWe have analysed 10 ks of XRT data for GRB 100728A (Cannizzo et al. GCN\nCirc. 11004), from 66 s to 23.4 ks after the BAT trigger. The data\ncomprise 1.3 ks in Windowed Timing (WT) mode (the first 9 s were taken\nwhile Swift was slewing) with the remainder in Photon Counting (PC)\nmode. The enhanced XRT position for this burst was given by Beardmore et\nal. (GCN. Circ 11005).\n\nThe light curve can be modeled with a broken power-law decay, with a\nseries of flares superimposed during the first kilosecond. The\nunderlying decay begins with a decay index of 1.6 (+/-0.1), breaking at\nT+410 sec to a decay index of 1.07 (+0.03, -0.04). The decay then breaks\nagain at T+11600 sec to a final decay of 1.82 (+/-0.2). Nine discrete\nflares can clearly be identified, with peak times of T+ 88, 111, 189,\n252, 296, 383, 445, 516, 659 sec. These all occurred while the XRT was \nin Windowed Timing mode.\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index of 2.022 (+/-0.022). The\nbest-fitting absorption column is 3.69 (+0.09, -0.08) x 10^21 cm^-2, in\nexcess of the Galactic value of 1.0 x 10^21 cm^-2 (Kalberla et al.\n2005). The PC mode spectrum has a photon index of 2.05 (+/-0.09) and a\nbest-fitting absorption column of 3.7 (+/-0.3) x 10^21 cm^-2. The counts\nto observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from\nthis spectrum is 4.5 x 10^-11 (7.6 x 10^-11) erg cm^-2 count^-1.\n\nIf the light curve continues to decay with a power-law decay index of\n1.82, the count rate at T+24 hours will be 0.024 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x\n10^-12 (1.8 x 10^-12) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00430151.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 11014,
  "createdOn": 1280324153000,
  "email": "pae9@star.le.ac.uk",
  "subject": "GRB 100728A: Swift-XRT refined analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@star.le.ac.uk>",
  "eventId": "GRB 100728A"
}