{
  "bibcode": "2013GCN.14479....1M",
  "body": "V. Mangano (INAF-IASFPA), D.N. Burrows (PSU), J.A. Kennea (PSU), M.C.\nStroh (PSU), B.P. Gompertz (U. Leicester), J.P. Osborne (U. Leicester),\nK.L. Page (U. Leicester), A. Melandri (INAF-OAB), B. Sbarufatti\n(INAF-OAB/PSU) and A. Maselli report on behalf of the Swift-XRT team:\n\nWe have analysed 7.3 ks of XRT data for GRB 130427B (Maselli  et al.\nGCN Circ. 14460),  from 67 s to 24.2 ks after the  BAT trigger. The\ndata comprise 120 s in Windowed Timing (WT) mode (the first 8 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 14467).\n\nThe late-time light curve (from T0+11.6 ks) can be modelled with  a\npower-law decay with a decay index of alpha=1.9 (+0.6, -0.5).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.93 (+0.14, -0.13). The\nbest-fitting absorption column is  8.3 (+2.8, -2.6) x 10^20 cm^-2, in\nexcess of the Galactic value of 4.4 x 10^20 cm^-2 (Kalberla et al.\n2005). The PC mode spectrum has a photon index of 1.79 (+0.23, -0.11)\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 3.9 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 (+4.7, -0) x 10^20 cm^-2\nGalactic foreground: 4.4 x 10^20 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     1.79 (+0.23, -0.11)\n\nIf the light curve continues to decay with a power-law decay index of\n1.9, the count rate at T+24 hours will be 9.7 x 10^-4 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.8 x\n10^-14 (4.2 x 10^-14) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00554635.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 14479,
  "createdOn": 1367112725000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 130427B: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 130427B"
}