{
  "bibcode": "2017GCN.20828....1D",
  "body": "P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), J.A.\nKennea (PSU), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), S.L.\nGibson (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U.\nLeicester) and\treport on behalf of the Swift-XRT team: report on\nbehalf of the Swift-XRT team:\n\nWe have analysed 6.7 ks of XRT data for GRB 170306A, from 119 s to 28.8\nks after the  BAT trigger. The data comprise 29 s in Windowed Timing\n(WT) mode (the first 8 s were taken while Swift was slewing) with the\nremainder in Photon Counting (PC) mode. The refined XRT position is RA,\nDec = 263.0690, -44.7482 which is equivalent to:\n\nRA (J2000): 17 32 16.56\nDec(J2000): -44 44 53.5\n\nwith an uncertainty of 3.6 arcsec (radius, 90% confidence).\n\nThe light curve can be modelled with an initial power-law decay with an\nindex of alpha=3.25 (+0.28, -0.21), followed by a break at T+559 s to\nan alpha of 0.36 (+0.10, -0.26).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 2.05 (+0.30, -0.19). The\nbest-fitting absorption column is  3.98 (+1.64, -0.16) x 10^21 cm^-2,\nconsistent with the Galactic value of 3.8 x 10^21 cm^-2 (Willingale et\nal. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux\nconversion factor deduced from this spectrum  is 3.8 x 10^-11 (6.1 x\n10^-11) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     3.98 (+1.64, -0.16) x 10^21 cm^-2\nGalactic foreground: 3.8 x 10^21 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     2.05 (+0.30, -0.19)\n\nIf the light curve continues to decay with a power-law decay index of\n0.36, the count rate at T+24 hours will be 0.011 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.3 x\n10^-13 (6.9 x 10^-13) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00741220.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 20828,
  "createdOn": 1488836186000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 170306A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 170306A"
}