{
  "bibcode": "2010GCN.10476....1D",
  "body": "A. de Ugarte Postigo, R. Margutti, B. Sbarufatti (INAF-OAB) and E. Troja\n(NASA/GSFC/ORAU) report on behalf of the Swift-XRT team:\n\nWe have analysed 2.5 ks of the Swift-XRT data for GRB 100305A (Troja\net al. GCN Circ. 10470), from 145 s to 6.0 ks after the  BAT trigger. The\ndata comprise 84 s in Windowed Timing (WT) mode with the remainder\nin Photon Counting (PC) mode.\n\nThe best position of the X-ray afterglow is the UVOT enhanced XRT\nposition given in Osborne et al. (GCN Circ. 10474).\n\nAnalysis of the light curve shows an initial steep power-law decay with\nan index of alpha=3.5 (+/-0.4), followed by a break at T+300 s to an\nalpha of 0.84 (+0.11, -0.58).\n\nA spectrum formed from the WT mode data can be fitted with an\nabsorbed power-law with a photon spectral index of 1.96 (+0.21,-0.20).\nThe best-fitting absorption column is  1.7 (+/-0.5) x 10^21 cm^-2, in\nexcess of the Galactic value of 2.1 x 10^20 cm^-2 (Kalberla et al.\n2005). The PC mode spectrum has a photon index of 2.14 (+0.24,-0.20)\nand a best-fitting absorption column of 1.7 (+0.60, -0.30) x 10^21\ncm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion\nfactor deduced from this spectrum  is 3.8 x 10^-11 (5.8 x 10^-11) erg\ncm^-2 count^-1.\n\nIf the light curve continues to decay with a power-law decay index of\n0.84, the count rate at T+24 hours will be 0.015 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.8 x\n10^-13 (8.7 x 10^-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/00414905.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 10476,
  "createdOn": 1267804481000,
  "email": "deugarte@iaa.es",
  "subject": "GRB 100305A: Swift-XRT refined analysis",
  "submitter": "Antonio Deugarte at IAA-CSIC  <deugarte@iaa.es>",
  "eventId": "GRB 100305A"
}