TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4080 SUBJECT: GRB051008: Swift XRT refined analysis DATE: 05/10/10 16:38:55 GMT FROM: Matteo Perri at ISAC/ASDC M. Perri, M. Capalbi (ASDC), D. N. Burrows, J. Kennea (PSU), D. Hinshaw (GSFC-SPSYS), P. Meszaros (PSU) report on behalf of the Swift XRT team: We have analysed the first 22 orbits of Swift XRT data for GRB 051008 (Marshall et al., GCN 4069). XRT observations began in Photon Counting (PC) mode 3038 seconds after the BAT trigger. The 0.3-10 keV light curve of the X-ray afterglow (Perri et al., GCN 4073) in the time interval 3-120 ks after the trigger is well fitted by a broken power-law model with decay indices alpha_1=-0.86+/-0.07, alpha_2=-2.0+/-0.1 and temporal break t_b=16.5+/-2.1 ks. The 0.3-10 keV X-ray spectrum in the time interval 3-40 ks after the trigger is well described by an absorbed power-law model with photon index Gamma=1.9+/-0.1. The derived NH is (3.1+/-0.5)E21 cm^-2, which is higher than the Galactic value (1.05E20 cm^-2, Dickey & Lockman 1990). Extrapolating the light curve at later times, we estimate the unabsorbed flux in the 0.3-10 keV energy band to be ~8E-14 ergs/s/cm^2 48 hours after the burst.