TITLE: GCN CIRCULAR NUMBER: 8767 SUBJECT: GRB 090102: Swift XRT refined analysis DATE: 09/01/02 16:30:08 GMT FROM: Vanessa Mangano at INAF-IASFPA V. Mangano, V. La Parola, B. Sbarufatti (INAF-IASF PA) report of behalf the Swift XRT team: We have analysed 6 orbits of Swift XRT data of GRB 090102 (Mangano et al. GCN Circ. 8762), consisting of 241 s in WT mode and 6.7 ks in PC mode. The XRT observation started 393 s after the trigger. The XRT light curve is well fitted by a single power-law with slope -1.32 +/- 0.01, and if decaying at this rate the source will reach a count rate level of 0.02 counts/s after one day. The WT spectrum is well fitted by an absorbed power-law with photon index 1.7 +/- 0.1, Galactic NH = 4.0e20 cm^-2 (Kalberla et al. 2005) and intrinsic absorption column of (3.8 +/- 2.0) e21 cm^-2 at the measured redshift z = 1.547 (De Ugarte Postigo et al. GCN Circ. 8766). The average observed [unabsorbed] flux during the WT observation is 6.2e-10 [7.2e-10] erg cm^-2 s^-1. The PC spectrum, extracted from about T+630 s to T+25 ks, is also well fitted by an absorbed power law with photon index 1.8 +/- 0.1, Galactic NH = 4.0e20 cm^-2 and and intrinsic NH = (7.0 +/- 2.0) e21 cm^-2 at z = 1.547. The average observed [unabsorbed] flux during the PC observation is 2.8e-11 [3.5e-11] erg cm^-2 s^-1. The rate to flux conversion factor is 1.3e-10 erg cm^-2 counts^-1. This is an official product of the Swift XRT team.