{
  "bibcode": "2013GCN.15356....1D",
  "body": "V. D'Elia (ASDC), A. Maselli  (INAF-IASFPA), J.A. Kennea (PSU), V.\nMangano (PSU), M.C. Stroh (PSU), A.P. Beardmore (U. Leicester), P.A.\nEvans (U. Leicester), B.P. Gompertz (U. Leicester) and A. Melandri\nreport on behalf of the Swift-XRT team:\n\nWe have analysed 11 ks of XRT data for GRB 131018A (Melandri  et al.\nGCN Circ. 15349),  from 119 s to 25.2 ks after the  BAT trigger. The\ndata comprise 171 s in Windowed Timing (WT) mode with the remainder in\nPhoton Counting (PC) mode. The enhanced XRT position for this burst was\ngiven by Goad et al. (GCN. Circ 15352).\n\nThe light curve can be modelled with an initial power-law decay with an\nindex of alpha=4.24 (+0.17, -0.15), followed by a break at T+549 s to\nan alpha of 0.30 (+/-0.06).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 3.06 (+0.13, -0.12). The\nbest-fitting absorption column is  4.3 (+/-0.3) x 10^21 cm^-2, in\nexcess of the Galactic value of 2.0 x 10^21 cm^-2 (Kalberla et al.\n2005). The PC mode spectrum has a photon index of 2.16 (+0.18, -0.17)\nand a best-fitting absorption column of 3.1 (+/-0.6) x 10^21 cm^-2. The\ncounts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 3.8 x 10^-11 (6.7 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     3.1 (+/-0.6) x 10^21 cm^-2\nGalactic foreground: 2.0 x 10^21 cm^-2\nExcess significance: 2.9 sigma\nPhoton index:\t     2.16 (+0.18, -0.17)\n\nIf the light curve continues to decay with a power-law decay index of\n0.30, the count rate at T+24 hours will be 0.040 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.5 x\n10^-12 (2.7 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/00574935.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 15356,
  "createdOn": 1382144464000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 131018A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 131018A"
}