TITLE: GCN CIRCULAR NUMBER: 11644 SUBJECT: GRB 110205A: Swift-XRT refined Analysis DATE: 11/02/05 13:47:05 GMT FROM: Kim Page at U.of Leicester A. P. Beardmore (U Leicester) reports on behalf of the Swift-XRT team: We have analysed 14 ks of XRT data for GRB 110205A (Beardmore et al. GCN Circ. 11629), from 145 s to 30.7 ks after the BAT trigger. The data comprise 737 s in Windowed Timing (WT) mode (the first 9 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN. Circ 11639). The light curve comprises a number of flares (at ~T0+145 s, T0+175 s to T0+275 s, T0+615 s) followed by a power-law decay. The late-time light curve (from T0+5.1 ks) can be modelled with a power-law decay with a decay index of alpha=1.63 (+/-0.10). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.420 (+/-0.020). The best-fitting absorption column is 4.2 (+/-0.6) x 10^21 cm^-2, at a redshift of 2.22, in addition to the Galactic value of 1.6 x 10^20 cm^-2 (Kalberla et al. 2005). The PC mode spectrum has a photon index of 1.99 (+0.08, -0.07) and a best-fitting absorption column of 3.5 (+1.6, -1.5) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.7 x 10^-11 (4.2 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Galactic foreground: 1.6 x 10^20 cm^-2 Intrinsic column: 3.5 (+1.6, -1.5) x 10^21 cm^-2 at z=2.22 Photon index: 1.99 (+0.08, -0.07) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00444643. This circular is an official product of the Swift-XRT team.