{
  "subject": "GRB 130408A: Swift-XRT refined Analysis",
  "eventId": "GRB 130408A",
  "bibcode": "2013GCN.14369....1D",
  "createdOn": 1365502263000,
  "circularId": 14369,
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "email": "pae9@leicester.ac.uk",
  "body": "V. D'Elia (ASDC), A. Maselli  (INAF-IASFPA), V. Mangano (INAF-IASFPA),\nJ.A. Kennea (PSU), M.C. Stroh (PSU), D.N. Burrows (PSU), A.P. Beardmore\n(U. Leicester), P.A. Evans (U. Leicester), B.P. Gompertz (U. Leicester)\nand A.Y. Lien report on behalf of the Swift-XRT team:\n\nWe have analysed 6.2 ks of XRT data for GRB 130408A (Lien  et al. GCN\nCirc. 14361),  from 134 s to 28.6 ks after the\tBAT trigger. The data\ncomprise 28 s in Windowed Timing (WT) mode (the first 9 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 14367).\n\nThe light curve can be modelled with a series of power-law decays. The\ninitial decay index is alpha=0.39 (+0.06, -0.07). At T+3999 s  the\ndecay steepens to an alpha of 8.0 (+0.0, -3.0) before breaking again at\nT+4518 s to a final decay with index alpha=0.97 (+0.14, -0.15).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 2.00 (+0.08, -0.07). The\nbest-fitting absorption column is  consistent with the Galactic value\nof 2.0 x 10^21 cm^-2 (Kalberla et al. 2005). The counts to observed\n(unabsorbed) 0.3-10 keV flux conversion factor deduced from this\nspectrum  is 3.9 x 10^-11 (5.6 x 10^-11) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nGalactic foreground: 2.0 x 10^21 cm^-2\nIntrinsic column:    0 (+4.9, -0) x 10^21 cm^-2 at z=3.758\nPhoton index:\t     2.00 (+0.08, -0.07)\n\nIf the light curve continues to decay with a power-law decay index of\n0.97, the count rate at T+24 hours will be 0.020 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.8 x\n10^-13 (1.1 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/00553132.\n\nThis circular is an official product of the Swift-XRT team."
}