TITLE: GCN CIRCULAR NUMBER: 12376 SUBJECT: GRB 110918A: Swift-XRT refined Analysis DATE: 11/09/21 16:04:56 GMT FROM: Vanessa Mangano at INAF-IASFPA V. Mangano (INAF-IASFPA), B. Sbarufatti (INAF-OAB/IASFPA), P. A. Evans (U Leicester), H. A. Krimm (GSFC/USRA) report on behalf of the Swift-XRT team: We have analysed 13.1 ks of XRT data for GRB 110918A, from 107.4 ks to 211.3 ks after the IPN trigger (Hurley et al. GCN Circ. 12357). The data are in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Mangano et al. (GCN Circ. 12364). The light curve can now be modeled with a single power-law decay with index alpha=1.49 (+0.24, -0.25). This confirms the XRT source is the afterglow of the GRB. The PC mode spectrum has a photon index of 2.11 (+0.21, -0.19) and a best-fitting absorption column at redshift z=0.982 (Levan et al. GCN Circ. 12368) of 6.3 (+2.8, -2.1) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.0 x 10^-11 (4.3 x 10^-11) erg cm^-2 count^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00020186. This circular is an official product of the Swift-XRT team.