{
  "bibcode": "2016GCN.20112....1D",
  "body": "A. D'Ai (INAF-IASFPA), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows\n(PSU), T.G.R. Roegiers (PSU), K.L. Page (U. Leicester), B. Mingo (U.\nLeicester), A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAB), P.\nD'Avanzo (INAF-OAB) and P.A. Evans (U. Leicester) report on behalf of\nthe Swift-XRT team:\n\nSwift-XRT has performed follow-up observations of the INTEGRAL-detected\nburst GRB 161023A (Gorbovskoy et al. GCN Circ. 20102), collecting 1.1\nks of Photon Counting (PC) mode data between T0+34.8 ks and T0+53.2 ks.\n\n\nA fading, uncatalogued X-ray source is detected consistent with the\nMASTER position (Gorbovskoy et al., GCN Circ. 20102) and is therefore\nbelieved to be the afterglow. Using 3643 s of PC mode data and 4 UVOT\nimages, we find an enhanced XRT position (using the XRT-UVOT alignment\nand matching UVOT field sources to the USNO-B1 catalogue): RA, Dec =\n311.02161, -47.66348 which is equivalent to:\n\nRA (J2000): 20h 44m 05.19s\nDec(J2000): -47d 39' 48.5\"\n\nwith an uncertainty of 1.5 arcsec (radius, 90% confidence). This\nposition is 0.2 arcsec from the MASTER position. \n\nThe light curve can be modelled with a power-law decay with a decay\nindex of alpha=2.3 (+0.9, -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 2.09 (+0.30, -0.16). The\nbest-fitting absorption column is  consistent with the Galactic value\nof 3.2 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed\n(unabsorbed) 0.3-10 keV flux conversion factor deduced from this\nspectrum  is 3.1 x 10^-11 (3.4 x 10^-11) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     3.2 (+/-5.6) x 10^20 cm^-2\nGalactic foreground: 3.2 x 10^20 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     2.09 (+0.30, -0.16)\n\nIf the light curve continues to decay with a power-law decay index of\n2.3, the count rate at T+24 hours will be 9.2 x 10^-3 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.8 x\n10^-13 (3.1 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/00020709.\nThe results of the full analysis of the XRT observations are available\nat http://www.swift.ac.uk/ToO_GRBs/00020709.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 20112,
  "createdOn": 1477330797000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 161023A: Swift-XRT afterglow detection",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 161023A"
}