TITLE: GCN CIRCULAR NUMBER: 11610 SUBJECT: GRB 110128A: Swift-XRT refined Analysis DATE: 11/01/28 15:29:47 GMT FROM: Dirk Grupe at PSU/Swift-XRT D. Grupe (PSU) reports on behalf of the Swift-XRT team: We have analyzed 11 ks of XRT data for GRB 110128A (Grupe et al. GCN Circ. 11603), from 125 s to 30.0 ks after the BAT trigger. The data comprise 9 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN. Circ 11606). The light curve can be modeled with an initial decay slope alpha-1 = 2.3+/-0.5 and a break at 700 (-200,+600) s followed by a decay slope of alpha-2 = 0.6+/-0.3. Currently we are in the plateau phase. At this point predictions of the behavior of the light curve are unreliable. A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.64 (+0.22, -0.21). The best-fitting absorption column is consistent with the Galactic value of 9.0 x 10^19 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.0 x 10^-11 (4.1 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Galactic foreground: 9.0 x 10^19 cm^-2 Intrinsic column: 0.0 (+3.0, -0.0) x 10^21 cm^-2 at z=2.339 Photon index: 1.64 (+0.22, -0.21) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00443861. This circular is an official product of the Swift-XRT team.