{
  "subject": "GRB 120923A: Swift-XRT refined Analysis",
  "eventId": "GRB 120923A",
  "bibcode": "2012GCN.13812....1K",
  "createdOn": 1348464485000,
  "circularId": 13812,
  "submitter": "Phil Evans at U of Leicester  <pae9@star.le.ac.uk>",
  "email": "pae9@star.le.ac.uk",
  "body": "J.A. Kennea (PSU), M.C. Stroh (PSU), D.N. Burrows (PSU), A.P. Beardmore\n(U. Leicester), P.A. Evans (U. Leicester), O.M. Littlejohns (U.\nLeicester), B. Sbarufatti (INAF-OAB/PSU), G. Stratta (ASDC), P.\nD'Avanzo (INAF-OAB) and V.N. Yershov report on behalf of the Swift-XRT\nteam:\n\nWe have analysed 9.0 ks of XRT data for GRB 120923A (Yershov  et al.\nGCN Circ. 13796), from 151 s to 57.5 ks after the  BAT trigger. The\ndata comprise 331 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 13801).\n\nThe light curve can be modelled with  a power-law decay with a decay\nindex of alpha=0.84 (+0.11, -0.09).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 1.78 (+0.47, -0.26). The\nbest-fitting absorption column is  1.08 (+1.30, -0.10) x 10^21 cm^-2,\nconsistent with the Galactic value of 9.8 x 10^20 cm^-2 (Kalberla et\nal. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux\nconversion factor deduced from this spectrum  is 4.2 x 10^-11 (5.1 x\n10^-11) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     1.08 (+1.30, -0.10) x 10^21 cm^-2\nGalactic foreground: 9.8 x 10^20 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     1.78 (+0.47, -0.26)\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00534402.\n\nThis circular is an official product of the Swift-XRT team."
}