{
  "bibcode": "2018GCN.23334....1O",
  "body": "J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), P. D'Avanzo\n(INAF-OAB), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), J.A. Kennea (PSU),\nB. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), A.P. Beardmore (U.\nLeicester) and P. D'Avanzo (INAF-OAB) report on behalf of the Swift-XRT\nteam:\n\nWe have analysed 190 s of Photon Counting (PC) mode XRT data for the\nSwift/BAT-detected burst GRB 181013A (D'Avanzo et al. GCN Circ. 23332),\ncollected between T0+115 s and T0+306 s. \n\nAn uncatalogued X-ray source is detected consistent with being within\n296 arcsec of the Swift/BAT position and is above the RASS limit and\nfading with 3-sigma significance, and is therefore likely the GRB\nafterglow.  The position of this source is RA, Dec=207.6518, +40.1082\nwhich is equivalent to:\n\nRA (J2000): 13:50:36.43\nDec(J2000): +40:06:29.5\n\nwith an uncertainty of 3.9 arcsec (radius, 90% confidence).  This\nposition is 4.8 arcmin from the Swift/BAT position. \n\nThe light curve can be modelled with a power-law decay with a decay\nindex of alpha=7.6 (+0.4, -1.0).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 0.98 (+0.30, -0.19). The\nbest-fitting absorption column is  consistent with the Galactic value\nof 9.4 x 10^19 cm^-2 (Willingale et al. 2013). The counts to observed\n(unabsorbed) 0.3-10 keV flux conversion factor deduced from this\nspectrum  is 6.2 x 10^-11 (6.2 x 10^-11) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     9 (+/-90) x 10^19 cm^-2\nGalactic foreground: 9.4 x 10^19 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     0.98 (+0.30, -0.19)\n\nIf the light curve continues to decay with a power-law decay index of\n7.6, the count rate at T+24 hours will be 5.9 x 10^-21 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.6 x\n10^-31 (3.6 x 10^-31) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis of the likely afterglow\nare at http://www.swift.ac.uk/ToO_GRBs/00866783/Source1.php.\nThe results of the full analysis of the XRT observations are available\nat http://www.swift.ac.uk/ToO_GRBs/00866783.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 23334,
  "createdOn": 1539414122000,
  "email": "paolo.davanzo@brera.inaf.it",
  "subject": "GRB 181013A: Swift-XRT afterglow detection",
  "submitter": "Paolo D'Avanzo at INAF-OAB  <paolo.davanzo@brera.inaf.it>",
  "eventId": "GRB 181013A"
}