{
  "circularId": 36538,
  "bibcode": "2024GCN.36538....1B",
  "eventId": "GRB 240523A",
  "createdOn": 1716510609239,
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "body": "R. Brivio (INAF-OAB), D.N. Burrows (PSU), J. D. Gropp (PSU), S.\nDichiara (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester),\nA. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAR) and P.A. Evans report on\nbehalf of the Swift-XRT team:\n\nWe have analysed 6.5 ks of XRT data for GRB 240523A, from 132 s to 27.6\nks after the  BAT trigger. The data comprise 8 s in Windowed Timing\n(WT) mode (taken while Swift was slewing), with the remainder in Photon\nCounting (PC) mode. \n\nThe light curve can be modelled with a series of power-law decays. The\ninitial decay index is alpha=2.8 (+0.6, -0.4). At T+400 s  the decay\nflattens to an alpha of -0.4 (+0.3, -0.5) before breaking again at\nT+2137 s to a final decay with index alpha=1.41 (+0.26, -0.24).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 2.06 (+0.24, -0.22). The\nbest-fitting absorption column is  1.1 (+0.6, -0.5) x 10^21 cm^-2, in\nexcess of the Galactic value of 1.6 x 10^20 cm^-2 (Willingale et al.\n2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion\nfactor deduced from this spectrum  is 3.3 x 10^-11 (4.2 x 10^-11) erg\ncm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     1.1 (+0.6, -0.5) x 10^21 cm^-2\nGalactic foreground: 1.6 x 10^20 cm^-2\nExcess significance: 2.9 sigma\nPhoton index:\t     2.06 (+0.24, -0.22)\n\nIf the light curve continues to decay with a power-law decay index of\n1.41, the count rate at T+24 hours will be 2.0 x 10^-3 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.5 x\n10^-14 (8.2 x 10^-14) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/01230423.\n\nThis circular is an official product of the Swift-XRT team.\n",
  "subject": "GRB 240523A: Swift-XRT refined Analysis",
  "submittedHow": "email"
}