{
  "bibcode": "2012GCN.13222....1E",
  "body": "P.A. Evans (U. Leicester), O.M. Littlejohns (U. Leicester), V. Mangano\n(INAF-IASFPA), A. Melandri (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU),\nM.C. Stroh (PSU), D.N. Burrows (PSU), J.A. Kennea (PSU), J.P. Osborne\n(U. Leicester) and G. Stratta report on behalf of the Swift-XRT team:\n\nWe have analysed 7.7 ks of XRT data for GRB 120404A (Stratta  et al.\nGCN Circ. 13208), from 119 s to 23.3 ks after the  BAT trigger. The\ndata comprise 109 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\nOsborne et al. (GCN. Circ 13218).\n\nThe light curve can be modelled with a series of power-law decays. The\ninitial decay index is alpha=2.15 (+0.18, -0.17). At T+544 s  the decay\nflattens to an alpha of 0.1 (+0.4, -0.6) before breaking again at\nT+2930 s to a final decay with index alpha=1.83 (+0.21, -0.19).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.72 (+0.14, -0.13). The\nbest-fitting absorption column is  2.3 (+4.7, -2.3) x 10^21 cm^-2, at a\nredshift of 2.87, in addition to the Galactic value of 3.4 x 10^20\ncm^-2 (Kalberla et al. 2005). The PC mode spectrum has a photon index\nof 1.90 (+/-0.12) and a best-fitting absorption column of 4.5 (+4.3,\n-4.0) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV\nflux conversion factor deduced from this spectrum  is 3.7 x 10^-11 (4.3\nx 10^-11) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nGalactic foreground: 3.4 x 10^20 cm^-2\nIntrinsic column:    4.5 (+4.3, -4.0) x 10^21 cm^-2 at z=2.87\nPhoton index:\t     1.90 (+/-0.12)\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00519380.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 13222,
  "createdOn": 1333587725000,
  "email": "pae9@star.le.ac.uk",
  "subject": "GRB 120404A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@star.le.ac.uk>",
  "eventId": "GRB 120404A"
}