{
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "createdOn": 1725616405645,
  "eventId": "GRB 240905E",
  "subject": "GRB 240905E: Swift-XRT refined Analysis",
  "bibcode": "2024GCN.37406....1F",
  "submittedHow": "email",
  "circularId": 37406,
  "body": "M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), A. D'Ai (INAF-IASFPA), M. A.\nWilliams (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), J.P. Osborne (U.\nLeicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester) and\nP.A. Evans report on behalf of the Swift-XRT team:\n\nWe have analysed 7.6 ks of XRT data for GRB 240905E, from 96 s to 50.6\nks after the  BAT trigger. The data comprise 146 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. The refined XRT position is RA,\nDec = 345.8021, +35.5227 which is equivalent to:\n\nRA (J2000): 23 03 12.51\nDec(J2000): +35 31 21.6\n\nwith an uncertainty of 4.1 arcsec (radius, 90% confidence).\n\nThe light curve can be modelled with an initial power-law decay with an\nindex of alpha=1.65 (+/-0.13), followed by a break at T+260 s to an\nalpha of 4.5 (+3.5, -0.4).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.25 (+/-0.10). The\nbest-fitting absorption column is  1.3 (+0.5, -0.4) x 10^21 cm^-2,\nconsistent with the Galactic value of 9.3 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 5.3 x 10^-11 (5.7 x\n10^-11) erg cm^-2 count^-1. \n\nA summary of the WT-mode spectrum is thus:\nTotal column:\t     1.3 (+0.5, -0.4) x 10^21 cm^-2\nGalactic foreground: 9.3 x 10^20 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     1.25 (+/-0.10)\n\nIf the light curve continues to decay with a power-law decay index of\n4.5, the count rate at T+24 hours will be 3.0 x 10^-11 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.6 x\n10^-21 (1.7 x 10^-21) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/01252695.\n\nThis circular is an official product of the Swift-XRT team.\n"
}