GCN Circular 8847
D. Grupe (PSU) reports on behalf of the Swift-XRT team: We have analyzed 7.7 ks of XRT data for GRB090123 (Grupe et al. GCN Circ. 8842), beginning 106 s after the BAT trigger. The data comprise 334 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 8843). The light curve can be modeled with an initial power-law decay with an index of alpha=1.78 (+0.06, -0.08), followed by a break at T+1530 (+720,-220) s to an alpha of 1.20 (+0.08, -0.10). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.65+/-0.05 with an absorption column fixed to the Galactic value of 1.79 x 1020 cm-2 (Kalberla et al. 2005). The PC mode spectrum has a photon index of 1.81+/-0.08 and an absorption column density also consistent with the Galactic value. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.2 x 10-11 (4.5 x 10-11) erg cm-2 count-1. If the light curve continues to decay with a power-law decay index of 1.20, the count rate at T+24 hours will be 0.0031 counts/s, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.3 x 10-13 (1.4 x 10-13) erg cm-2 s-1.