{
  "bibcode": "2020GCN.27312....1E",
  "body": "P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U.\nLeicester), M.G. Bernardini (INAF-OAB), E. Ambrosi  (INAF-IASFPA) , M.\nCapalbi (INAF-IASFPA), A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU),\nD.N. Burrows (PSU) and S.B. Cenko report on behalf of the Swift-XRT\nteam:\n\nWe have analysed 6.6 ks of XRT data for GRB 200303A (Cenko et al. GCN\nCirc. 27297), from 77 s to 41.6 ks after the  BAT trigger. The data\ncomprise 582 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 Goad et al.\n(GCN Circ. 27300).\n\nThe late-time light curve (from T0+4.8 ks) can be modelled with a\npower-law decay with a decay index of alpha=1.27 (+0.09, -0.10).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 2.41 (+/-0.05). The\nbest-fitting absorption column is  1.10 (+0.05, -0.04) x 10^22 cm^-2,\nin excess of the Galactic value of 1.6 x 10^20 cm^-2 (Willingale et al.\n2013). The PC mode spectrum has a photon index of 2.38 (+0.15, -0.14)\nand a best-fitting absorption column of 7.5 (+1.0, -0.9) x 10^21 cm^-2.\nThe counts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 3.7 x 10^-11 (8.8 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     7.5 (+1.0, -0.9) x 10^21 cm^-2\nGalactic foreground: 1.6 x 10^20 cm^-2\nExcess significance: 13.4 sigma\nPhoton index:\t     2.38 (+0.15, -0.14)\n\nIf the light curve continues to decay with a power-law decay index of\n1.27, the count rate at T+24 hours will be 0.043 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.6 x\n10^-12 (3.8 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/00959431.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 27312,
  "createdOn": 1583262732000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 200303A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 200303A"
}