{
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "eventId": "GRB 230911C",
  "bibcode": "2023GCN.34676....1M",
  "subject": "GRB 230911C: Swift-XRT refined Analysis",
  "circularId": 34676,
  "createdOn": 1694519152669,
  "body": "A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB),\nJ.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), D.N. Burrows (PSU), J.P.\nOsborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U.\nLeicester) and P.A. Evans report on behalf of the Swift-XRT team:\n\nWe have analysed 7.2 ks of XRT data for GRB 230911C, from 103 s to 74.1\nks after the  BAT trigger. The data comprise 106 s in Windowed Timing\n(WT) mode (the first 9 s were taken while Swift was slewing) with the\nremainder in Photon Counting (PC) mode. \n\nThe late-time light curve (from T0+4.2 ks) can be modelled with a\npower-law decay with a decay index of alpha=0.48 (+0.22, -0.18).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 1.86 (+0.26, -0.21). The\nbest-fitting absorption column is  1.3 (+0.9, -0.3) x 10^21 cm^-2,\nconsistent with the Galactic value of 9.4 x 10^20 cm^-2 (Willingale et\nal. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux\nconversion factor deduced from this spectrum  is 3.6 x 10^-11 (4.4 x\n10^-11) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     1.3 (+0.9, -0.3) x 10^21 cm^-2\nGalactic foreground: 9.4 x 10^20 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     1.86 (+0.26, -0.21)\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/01191188.\n\nThis circular is an official product of the Swift-XRT team.\n",
  "submittedHow": "email"
}