{
  "submittedHow": "email",
  "bibcode": "2024GCN.35469....1G",
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "eventId": "GRB 240102A",
  "body": "J. D. Gropp (PSU), J.P. Osborne (U. Leicester), K.L. Page (U.\nLeicester), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), P. D'Avanzo\n(INAF-OAB), S. Dichiara (PSU), J.A. Kennea (PSU) and P.A. Evans report\non behalf of the Swift-XRT team:\n\nWe have analysed 6.6 ks of XRT data for GRB 240102A, from 113 s to 28.3\nks after the  BAT trigger. The data comprise 91 s in Windowed Timing\n(WT) mode (the first 10 s were taken while Swift was slewing) with the\nremainder in Photon Counting (PC) mode. The best available XRT position\n (using the promptly downlinked event data, the XRT-UVOT alignment and\nmatching UVOT field sources to the USNO-B1 catalogue) is RA, Dec =\n96.83800, -20.04076 which is equivalent to:\n\nRA (J2000): 06 27 21.12\nDec(J2000): -20 02 26.7\n\nwith an uncertainty of 1.9 arcsec (radius, 90% confidence).\n\nThe late-time light curve (from T0+4.7 ks) can be modelled with a\npower-law decay with a decay index of alpha=0.5 (+/-0.3).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.74 (+0.11, -0.10). The\nbest-fitting absorption column is  3.3 (+0.6, -0.5) x 10^21 cm^-2, in\nexcess of the Galactic value of 2.3 x 10^21 cm^-2 (Willingale et al.\n2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion\nfactor deduced from this spectrum  is 4.3 x 10^-11 (5.7 x 10^-11) erg\ncm^-2 count^-1. \n\nA summary of the WT-mode spectrum is thus:\nTotal column:\t     3.3 (+0.6, -0.5) x 10^21 cm^-2\nGalactic foreground: 2.3 x 10^21 cm^-2\nExcess significance: 3.1 sigma\nPhoton index:\t     1.74 (+0.11, -0.10)\n\nIf the light curve continues to decay with a power-law decay index of\n0.5, the count rate at T+24 hours will be 9.8 x 10^-3 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.2 x\n10^-13 (5.6 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/01205899.\n\nThis circular is an official product of the Swift-XRT team.\n",
  "circularId": 35469,
  "createdOn": 1704265254588,
  "subject": "GRB 240102A: Swift-XRT refined Analysis"
}