{
  "bibcode": "2013GCN.15417....1M",
  "body": "A. Melandri (INAF-OAB), M.C. Stroh (PSU), D.N. Burrows (PSU), J.A.\nKennea (PSU), B.P. Gompertz (U. Leicester), J.P. Osborne (U.\nLeicester), K.L. Page (U. Leicester), B. Sbarufatti (INAF-OAB/PSU), P.\nD'Avanzo (INAF-OAB) and E. Troja report on behalf of the Swift-XRT\nteam:\n\nWe have analysed 6.9 ks of XRT data for GRB 131030A (Troja  et al. GCN\nCirc. 15402),  from 68 s to 41.4 ks after the  BAT trigger. The data\ncomprise 1.0 ks 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 Evans et\nal. (GCN. Circ 15416).\n\nThe late-time light curve (from T0+4.3 ks) can be modelled with  a\npower-law decay with a decay index of alpha=1.18 (+0.06, -0.07).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 2.11 (+/-0.03). The\nbest-fitting absorption column is  1.17 (+/-0.07) x 10^21 cm^-2, in\nexcess of the Galactic value of 4.7 x 10^20 cm^-2 (Kalberla et al.\n2005). The PC mode spectrum has a photon index of 2.09 (+0.13, -0.12)\nand a best-fitting absorption column of 1.16 (+0.30, -0.28) x 10^21\ncm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion\nfactor deduced from this spectrum  is 3.5 x 10^-11 (4.7 x 10^-11) erg\ncm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     1.16 (+0.30, -0.28) x 10^21 cm^-2\nGalactic foreground: 4.7 x 10^20 cm^-2\nExcess significance: 4.0 sigma\nPhoton index:\t     2.09 (+0.13, -0.12)\n\nIf the light curve continues to decay with a power-law decay index of\n1.18, the count rate at T+24 hours will be 0.055 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.9 x\n10^-12 (2.6 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/00576238.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 15417,
  "createdOn": 1383228543000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 131030A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 131030A"
}