{
  "bibcode": "2023GCN.34444....1D",
  "eventId": "GRB 230815A",
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "body": "P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), D.N. Burrows (PSU),\nJ. D. Gropp (PSU), S. Dichiara (PSU), J.P. Osborne (U. Leicester), K.L.\nPage (U. Leicester), A.P. Beardmore (U. Leicester), E. Ambrosi \n(INAF-IASFPA)  and P.A. Evans report on behalf of the Swift-XRT team:\n\nWe have analysed 6.0 ks of XRT data for GRB 230815A, from 117 s to 45.2\nks after the  BAT trigger. The data comprise 574 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+6.1 ks) can be modelled with a\npower-law decay with a decay index of alpha=1.94 (+0.25, -0.29).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.92 (+0.06, -0.05). The\nbest-fitting absorption column is  7.4 (+0.5, -0.4) x 10^21 cm^-2, in\nexcess of the Galactic value of 4.9 x 10^21 cm^-2 (Willingale et al.\n2013). The PC mode spectrum has a photon index of 1.94 (+0.18, -0.17)\nand a best-fitting absorption column of 9.1 (+1.7, -1.5) x 10^21 cm^-2.\nThe counts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 4.9 x 10^-11 (8.5 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     9.1 (+1.7, -1.5) x 10^21 cm^-2\nGalactic foreground: 4.9 x 10^21 cm^-2\nExcess significance: 4.5 sigma\nPhoton index:\t     1.94 (+0.18, -0.17)\n\nIf the light curve continues to decay with a power-law decay index of\n1.94, the count rate at T+24 hours will be 2.5 x 10^-3 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.2 x\n10^-13 (2.1 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/01185505.\n\nThis circular is an official product of the Swift-XRT team.\n",
  "subject": "GRB 230815A: Swift-XRT refined Analysis",
  "createdOn": 1692163013875,
  "submittedHow": "email",
  "circularId": 34444
}