{
  "bibcode": "2015GCN.17668....1B",
  "body": "D.N. Burrows (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU),\nA.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), A.\nAmaral-Rogers (U. Leicester), A. Maselli  (INAF-IASFPA), A. Melandri\n(INAF-OAB), P. D'Avanzo (INAF-OAB) and A.Y. Lien report on behalf of\nthe Swift-XRT team:\n\nWe have analysed 10 ks of XRT data for GRB 150403A (Lien et al. GCN\nCirc. 17665), from 64 s to 30.5 ks after the  BAT trigger. The data\ncomprise 3.5 ks in Windowed Timing (WT) mode (the first 8 s were taken\nwhile Swift was slewing) with the remainder in Photon Counting (PC)\nmode. The enhanced XRT position for this burst was given by Beardmore\net al. (GCN Circ. 17666).\n\nThe late-time light curve (from T0+5.1 ks) can be modelled with a\nseries of power-law decays. The initial decay index is alpha=1.14\n(+0.08, -0.15). At T+6776 s  the decay steepens to an alpha of 8.0\n(+0.0, -2.7) before breaking again at T+7063 s to a final decay with\nindex alpha=1.42 (+0.14, -0.22).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.695 (+/-0.016). The\nbest-fitting absorption column is  1.03 (+/-0.05) x 10^21 cm^-2, in\nexcess of the Galactic value of 5.3 x 10^20 cm^-2 (Willingale et al.\n2013). The PC mode spectrum has a photon index of 1.66 (+/-0.10) and a\nbest-fitting absorption column of 1.1 (+/-0.3) x 10^21 cm^-2. The\ncounts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 4.1 x 10^-11 (4.7 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     1.1 (+/-0.3) x 10^21 cm^-2\nGalactic foreground: 5.3 x 10^20 cm^-2\nExcess significance: 2.9 sigma\nPhoton index:\t     1.66 (+/-0.10)\n\nIf the light curve continues to decay with a power-law decay index of\n1.42, the count rate at T+24 hours will be 0.16 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.7 x\n10^-12 (7.7 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/00637044.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 17668,
  "createdOn": 1428142623000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 150403A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 150403A"
}