{
  "bibcode": "2013GCN.14749....1K",
  "body": "J.A. Kennea (PSU), M.C. Stroh (PSU), D.N. Burrows (PSU), A.P. Beardmore\n(U. Leicester), P.A. Evans (U. Leicester), B.P. Gompertz (U.\nLeicester), G. Stratta (ASDC), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC)\nand A. Melandri report on behalf of the Swift-XRT team:\n\nWe have analysed 6.6 ks of XRT data for GRB 130603B (Melandri  et al.\nGCN Circ. 14735),  from 43 s to 28.2 ks after the  BAT trigger. The\ndata comprise 378 s in Windowed Timing (WT) mode (the first 9 s were\ntaken while Swift was slewing) with the remainder in Photon Counting\n(PC) mode. The enhanced XRT position for this burst was given by Evans\net al. (GCN. Circ 14739).\n\nThe light curve can be modelled with an initial power-law decay with an\nindex of alpha=0.35 (+0.08, -0.09), followed by a break at T+2404 s to\nan alpha of 1.46 (+0.13, -0.12).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.97 (+0.23, -0.22). The\nbest-fitting absorption column is  2.8 (+1.0, -0.8) x 10^21 cm^-2, in\nexcess of the Galactic value of 1.9 x 10^20 cm^-2 (Kalberla et al.\n2005). The PC mode spectrum has a photon index of 2.21 (+0.18, -0.17)\nand a best-fitting absorption column of 2.5 (+/-0.5) x 10^21 cm^-2. The\ncounts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 3.6 x 10^-11 (6.2 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     2.5 (+/-0.5) x 10^21 cm^-2\nGalactic foreground: 1.9 x 10^20 cm^-2\nExcess significance: 7.7 sigma\nPhoton index:\t     2.21 (+0.18, -0.17)\n\nIf the light curve continues to decay with a power-law decay index of\n1.46, the count rate at T+24 hours will be 4.7 x 10^-3 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.7 x\n10^-13 (2.9 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/00557310.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 14749,
  "createdOn": 1370319304000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 130603B: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 130603B"
}