TITLE: GCN CIRCULAR NUMBER: 20092 SUBJECT: GRB 161022A: Swift-XRT refined Analysis DATE: 16/10/22 12:26:37 GMT FROM: Phil Evans at U of Leicester V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), B. Mingo (U. Leicester), A. Melandri (INAF-OAB) and M. Stamatikos report on behalf of the Swift-XRT team: We have analysed 8.7 ks of XRT data for GRB 161022A (Stamatikos et al. GCN Circ. 20087), from 118 s to 22.5 ks after the BAT trigger. The data comprise 7 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder 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 = 129.0017, 54.3486 which is equivalent to: RA (J2000): 08 36 00.40 Dec(J2000): +54 20 55.0 with an uncertainty of 2.0 arcsec (radius, 90% confidence). The light curve can be modelled with a power-law decay with a decay index of alpha=1.46 (+0.13, -0.11). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.70 (+0.16, -0.07). The best-fitting absorption column is consistent with the Galactic value of 4.1 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.8 x 10^-11 (4.0 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 4.1 (+/-2.0) x 10^20 cm^-2 Galactic foreground: 4.1 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.70 (+0.16, -0.07) If the light curve continues to decay with a power-law decay index of 1.46, the count rate at T+24 hours will be 1.5 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.6 x 10^-15 (5.9 x 10^-15) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00718655. This circular is an official product of the Swift-XRT team.