TITLE: GCN CIRCULAR NUMBER: 23418 SUBJECT: GRB 181110A: Swift-XRT refined Analysis DATE: 18/11/10 18:09:21 GMT FROM: Phil Evans at U of Leicester B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), A. Tohuvavohu (PSU) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 7.4 ks of XRT data for GRB 181110A (Evans et al. GCN Circ. 23413), from 67 s to 24.8 ks after the BAT trigger. The data comprise 260 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN Circ. 23417). The late-time light curve (from T0+5.2 ks) can be modelled with a power-law decay with a decay index of alpha=2.10 (+/-0.14). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.88 (+/-0.04). The best-fitting absorption column is 8.6 (+1.0, -0.9) x 10^20 cm^-2, consistent with the Galactic value of 7.7 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.74 (+0.07, -0.06) and a best-fitting absorption column consistent with the Galactic value. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.8 x 10^-11 (4.3 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 7.7 (+1.5, -0.0) x 10^20 cm^-2 Galactic foreground: 7.7 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.74 (+0.07, -0.06) If the light curve continues to decay with a power-law decay index of 2.10, the count rate at T+24 hours will be 2.2 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.3 x 10^-14 (9.3 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/00871316. This circular is an official product of the Swift-XRT team.