TITLE: GCN CIRCULAR NUMBER: 16941 SUBJECT: GRB 141022A: Swift-XRT refined Analysis DATE: 14/10/22 13:48:04 GMT FROM: Phil Evans at U of Leicester P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), M. de Pasquale (INAF-IASFPA), M.C. Stroh (PSU), D.N. Burrows (PSU), J.A. Kennea (PSU), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), B.P. Gompertz (U. Leicester) and A. Vargas report on behalf of the Swift-XRT team: We have analysed 10 ks of XRT data for GRB 141022A (Vargas et al. GCN Circ. 16938), from 144 s to 25.5 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The best available XRT position (using the promptly downlinked event data, the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue) is RA, Dec = 241.8696, -72.1254 which is equivalent to: RA (J2000): 16 07 28.70 Dec(J2000): -72 07 31.4 with an uncertainty of 2.1 arcsec (radius, 90% confidence). The light curve can be modelled with a power-law decay with a decay index of alpha=1.21 (+/-0.08). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.5 (+0.5, -0.4). The best-fitting absorption column is 1.1 (+0.5, -0.4) x 10^22 cm^-2, in excess of the Galactic value of 1.0 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.9 x 10^-11 (1.2 x 10^-10) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.1 (+0.5, -0.4) x 10^22 cm^-2 Galactic foreground: 1.0 x 10^21 cm^-2 Excess significance: 4.5 sigma Photon index: 2.5 (+0.5, -0.4) If the light curve continues to decay with a power-law decay index of 1.21, the count rate at T+24 hours will be 2.7 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.0 x 10^-14 (3.3 x 10^-14) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00616061. This circular is an official product of the Swift-XRT team.