TITLE: GCN CIRCULAR NUMBER: 10106 SUBJECT: GRB 091029: Swift XRT refined analysis DATE: 09/10/29 19:46:14 GMT FROM: Dirk Grupe at PSU/Swift-XRT D. Grupe (PSU) reports on behalf of the Swift-XRT team: We have analyzed the first 7 orbits of XRT data of GRB 091029 (Grupe et al. GCN Circ. 10097). The data comprise 69 s in Windowed Timing (WT) mode and 15727 s in Photon Counting (PC) mode. The enhanced XRT position has already been determined by Goad et al. (GCN circ. 10102). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.30+/-0.08 with an absorption column density consistent with the Galactic value of 1.14 x 10^20 cm^-2 (Kalberla et al. 2005). The PC mode spectrum (excluding the flare around 300 s after the burst) results in a slightly flatter X-ray spectrum with Gamma = 2.00+/-0.07. The light curve (excluding the flares) can be modelled with a double broken power-law decay with an initial decay slope alpha-1 = 3.76+0.21-0.19 with the first break at 358+48-31 s after the trigger followed by a plateau phase with a decay slope alpha-2 = -0.17+/-0.22 and a second break at 3640+3450-1270 s. After this break the decay slope is alpha-3 = 0.76+0.06-0.05. If the afterglow continues to decay with a slope of 0.76, the predicted count rates 24, 48, and 72 hours after the trigger are 0.033 counts s^-1 or 1.12e-12 ergs s^-1 cm^-2, 0.020 counts s^-1 or 6.80e-13 ergs s^-1 cm^-2, 0.014 counts s^-1 or 4.76e-13 ergs s^-1 cm^-2, respectively. This circular is an official product of the Swift-XRT team.