GCN Circular 12141
G. Stratta (ASDC), V. D'Elia (ASDC) and S. T. Holland (CRESST/USRA/GSFC) report on behalf of the Swift-XRT team: We have analysed 9.6 ks of XRT data for GRB 110709A (Holland et al. GCN Circ. 12118), from 71 s to 19.3 ks after the BAT trigger. The data comprise 565 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN. Circ 12119). The late-time light curve (from T0+5.2 ks) can be modelled with a power-law decay with a decay index of alpha=1.72 (+/-0.10). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.21 (+0.09, -0.08). The best-fitting absorption column is 7.5 (+0.6, -0.5) x 10^21 cm^-2, in excess of the Galactic value of 1.5 x 10^20 cm^-2 (Kalberla et al. 2005). The PC mode spectrum has a photon index of 2.07 (+/-0.11) and a best-fitting absorption column of 7.3 (+/-0.7) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 5.0 x 10^-11 (1.0 x 10^-10) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 7.3 (+/-0.7) x 10^21 cm^-2 Galactic foreground: 1.5 x 10^20 cm^-2 Excess significance: 17.8 sigma Photon index: 2.07 (+/-0.11) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00456939. This circular is an official product of the Swift-XRT team.