{
  "bibcode": "2010GCN.10733....1M",
  "body": "R. Margutti, B. Sbarufatti, A. de Ugarte Postigo (INAF-OAB)\nreport on behalf of the Swift-XRT team:\n\nWe have analysed 3.0 ks of XRT data for GRB 100508A (Margutti et al.\nGCN Circ. 10728), from 132 s to 7.3 ks after the BAT trigger. The data\ncomprise 40 s in Windowed Timing (WT) mode (the first 9 s were taken while\nSwift was slewing) with the remainder in Photon Counting (PC) mode.\nThe UVOT-enhanced XRT position was given by Beardmore al. in GCN Circ. \n10731.\n\nThe light curve can be modelled with an initial power-law decay with an \nindex\nof alpha=1.49 (+0.22, -0.18), followed by a break at T+694 s\nto an alpha=0.39 (+0.08, -0.09).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed \npower-law\nwith a photon spectral index of 1.66 (+0.28, -0.27). The best-fitting \nabsorption column\nis 1.4 (+0.9, -0.7) x 10^21 cm^-2, in excess of the Galactic value of\n2.4 x 10^20 cm^-2 (Kalberla et al. 2005). Uncertainties are given at 90% \nc.l.\nThe counts to observed (unabsorbed) 0.3-10 keV flux conversion factor \ndeduced from\nthis spectrum is 4.7 x 10^-11 (5.7 x 10^-11) erg cm^-2 count^-1.\n\nIf the light curve continues to decay with a power-law decay index of \n0.39, the count\nrate at T+24 hours will be 0.068 count s^-1, corresponding to an \nobserved (unabsorbed)\n0.3-10 keV flux of 3.2 x 10^-12 (3.9 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/00421386.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 10733,
  "createdOn": 1273334826000,
  "email": "raffaella.margutti@brera.inaf.it",
  "subject": "GRB 100508A: Swift-XRT Refined analysis",
  "submitter": "Raffaella Margutti at U. di Milano Bicocca  <raffaella.margutti@brera.inaf.it>",
  "eventId": "GRB 100508A"
}