{
  "bibcode": "2012GCN.13187....1E",
  "body": "P.A. Evans (U. Leicester), O.M. Littlejohns (U. Leicester), A. Maselli \n(INAF-IASFPA), V. Mangano (INAF-IASFPA), A. Melandri (INAF-OAB), J.A.\nKennea (PSU), M.C. Stroh (PSU), D.N. Burrows (PSU) and A.P. Beardmore\nreport on behalf of the Swift-XRT team:\n\nWe have analysed 10 ks of XRT data for GRB 120401A (Beardmore  et al.\nGCN Circ. 13182), from 124 s to 24.8 ks after the  BAT trigger. The\ndata comprise 519 s in Windowed Timing (WT) mode with the remainder in\nPhoton Counting (PC) mode. The enhanced XRT position for this burst was\ngiven by Evans et al. (GCN. Circ 13183).\n\nThe late-time light curve (from T0+5.0 ks) can be modelled with  a\npower-law decay with a decay index of alpha=1.2 (+0.4, -0.3).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 2.29 (+0.07, -0.06). The\nbest-fitting absorption column is  1.27 (+0.13, -0.12) x 10^21 cm^-2,\nin excess of the Galactic value of 3.2 x 10^20 cm^-2 (Kalberla et al.\n2005). The PC mode spectrum has a photon index of 1.75 (+0.11, -0.10)\nand a best-fitting absorption column consistent with the Galactic\nvalue. The counts to observed (unabsorbed) 0.3-10 keV flux conversion\nfactor deduced from this spectrum  is 4.0 x 10^-11 (4.3 x 10^-11) erg\ncm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     0 (+1.5, -0) x 10^20 cm^-2\nGalactic foreground: 3.2 x 10^20 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     1.75 (+0.11, -0.10)\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00519043.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 13187,
  "createdOn": 1333301645000,
  "email": "pae9@star.le.ac.uk",
  "subject": "GRB 120401A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@star.le.ac.uk>",
  "eventId": "GRB 120401A"
}