{
  "bibcode": "2023GCN.35218....1B",
  "createdOn": 1701290131738,
  "body": "D.N. Burrows (PSU), J. D. Gropp (PSU), S. Dichiara (PSU), J.P. Osborne\n(U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U.\nLeicester), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E.\nAmbrosi  (INAF-IASFPA)\tand P.A. Evans report on behalf of the\nSwift-XRT team:\n\nWe have analysed 7.0 ks of XRT data for GRB 231129A, from 115 s to 43.8\nks after the  BAT trigger. The data comprise 174 s in Windowed Timing\n(WT) mode with the remainder in Photon Counting (PC) mode. The refined\nXRT position is RA, Dec = 317.5437, +41.5206 which is equivalent to:\n\nRA (J2000): 21 10 10.49\nDec(J2000): +41 31 14.2\n\nwith an uncertainty of 3.5 arcsec (radius, 90% confidence).\n\nThe light curve can be modelled with a series of power-law decays. The\ninitial decay index is alpha=4.86 (+/-0.21). At T+165 s  the decay\nsteepens to an alpha of 6.44 (+0.28, -0.24) before breaking again at\nT+308 s to a final decay with index alpha=0.83 (+0.05, -0.06).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.83 (+/-0.07). The\nbest-fitting absorption column is  1.09 (+/-0.08) x 10^22 cm^-2, in\nexcess of the Galactic value of 5.9 x 10^21 cm^-2 (Willingale et al.\n2013). The PC mode spectrum has a photon index of 2.18 (+0.31, -0.29)\nand a best-fitting absorption column of 1.6 (+/-0.4) x 10^22 cm^-2. The\ncounts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 5.0 x 10^-11 (1.2 x 10^-10) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     1.6 (+/-0.4) x 10^22 cm^-2\nGalactic foreground: 5.9 x 10^21 cm^-2\nExcess significance: 4.5 sigma\nPhoton index:\t     2.18 (+0.31, -0.29)\n\nIf the light curve continues to decay with a power-law decay index of\n0.83, the count rate at T+24 hours will be 0.014 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.2 x\n10^-13 (1.8 x 10^-12) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/01199764.\n\nThis circular is an official product of the Swift-XRT team.\n",
  "subject": "GRB 231129A: Swift-XRT refined Analysis",
  "submittedHow": "email",
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "eventId": "GRB 231129A",
  "circularId": 35218
}