{
  "bibcode": "2018GCN.23374....1M",
  "body": "A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), A. Tohuvavohu (PSU), S.\nJ. LaPorte (PSU), J.A. Kennea (PSU), P.A. Evans (U. Leicester), J.P.\nOsborne (U. Leicester), K.L. Page (U. Leicester), V. D'Elia (ASDC) and\nF.E. Marshall report on behalf of the Swift-XRT team:\n\nWe have analysed 2.0 ks of XRT data for GRB 181022A (Marshall et al.\nGCN Circ. 23364), from 106 s to 5.4 ks after the  BAT trigger. The data\nare entirely in Photon Counting (PC) mode. The best available XRT\nposition  (using the promptly downlinked event data, the XRT-UVOT\nalignment and matching UVOT field sources to the USNO-B1 catalogue) is\nRA, Dec = 56.7920, -29.3798 which is equivalent to:\n\nRA (J2000): 03 47 10.09\nDec(J2000): -29 22 47.2\n\nwith an uncertainty of 2.1 arcsec (radius, 90% confidence).\n\nThe light curve can be modelled with a power-law decay with a decay\nindex of alpha=1.73 (+/-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 1.7 (+/-0.5). The\nbest-fitting absorption column is  2.9 (+2.9, -1.9) x 10^21 cm^-2, in\nexcess of the Galactic value of 8.8 x 10^19 cm^-2 (Willingale et al.\n2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion\nfactor deduced from this spectrum  is 4.4 x 10^-11 (5.7 x 10^-11) erg\ncm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     2.9 (+2.9, -1.9) x 10^21 cm^-2\nGalactic foreground: 8.8 x 10^19 cm^-2\nExcess significance: 2.5 sigma\nPhoton index:\t     1.7 (+/-0.5)\n\nIf the light curve continues to decay with a power-law decay index of\n1.73, the count rate at T+24 hours will be 1.2 x 10^-5 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.4 x\n10^-16 (7.1 x 10^-16) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00868312.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 23374,
  "createdOn": 1540317243000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 181022A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 181022A"
}