{
  "createdOn": 1727876636505,
  "bibcode": "2024GCN.37681....1O",
  "circularId": 37681,
  "eventId": "GRB 241002A",
  "submittedHow": "email",
  "body": "J.P. Osborne (U. Leicester), M. Capalbi (INAF-IASFPA), M. Perri (SSDC &\nINAF-OAR), V. D'Elia (SSDC & INAF-OAR), M. A. Williams (PSU), S.\nDichiara (PSU), J.A. Kennea (PSU), K.L. Page (U. Leicester), A.P.\nBeardmore (U. Leicester) and P.A. Evans report on behalf of the\nSwift-XRT team:\n\nWe have analysed 10 ks of XRT data for GRB 241002A, from 95 s to 38.9\nks after the  BAT trigger. The data comprise 212 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 light curve can be modelled with a series of power-law decays. The\ninitial decay index is alpha=0.8 (+1.1, -1.8). At T+122 s  the decay\nsteepens to an alpha of 5.1 (+/-0.7) before breaking again at T+268 s\nto a final decay with index alpha=0.57 (+0.12, -0.18).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 3.1 (+/-0.3). The\nbest-fitting absorption column is  1.01 (+0.21, -0.19) x 10^22 cm^-2,\nin excess of the Galactic value of 1.4 x 10^20 cm^-2 (Willingale et al.\n2013). The PC mode spectrum has a photon index of 2.1 (+0.5, -0.4) and\na best-fitting absorption column of 8.6 (+4.2, -3.4) x 10^21 cm^-2. The\ncounts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 4.3 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     8.6 (+4.2, -3.4) x 10^21 cm^-2\nGalactic foreground: 1.4 x 10^20 cm^-2\nExcess significance: 4.1 sigma\nPhoton index:\t     2.1 (+0.5, -0.4)\n\nIf the light curve continues to decay with a power-law decay index of\n0.57, 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 4.6 x\n10^-13 (9.3 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/01257556.\n\nThis circular is an official product of the Swift-XRT team.\n",
  "subject": "GRB 241002A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>"
}