TITLE: GCN CIRCULAR NUMBER: 8481 SUBJECT: GRB 081104: refined XRT analysis DATE: 08/11/05 11:11:44 GMT FROM: Vanessa Mangano at INAF-IASFPA V. Mangano, V. La Parola, B. Sbarufatti (INAF-IASF PA) report on behalf the Swift-XRT Team: Swift XRT follow-up observation of the field of GRB 081104 (trigger=333666, Parsons et al., GCN Circ. 8473) started on 2008 11 04 at 10:18:45 UT (about 40 min after the trigger). We have analysed the first four orbits of PC mode XRT data accumulated from T+2640 s to T+22153 s (6.5 ks exposure). The light curve of the X-ray source given in Mangano e. at, GCN Circ. 8474 shows a power-law decay with slope -1.0 +/- 0.2, with an initial count rate at the level of 0.1 counts/s. If decaying at this rate the source will reach a count rate level of 3.e-3 counts/s at T+24 hours. The average spectrum of the source have been fitted with Cash statistics. It can be modeled with a highly absorbed power law, with NH=(1.5 +/ -0.4)e22 cm^-2 (significantly in excess with respect to the Galactic absorption along the line of sight, of 7.0e20 cm^-2; Kalberla et al. 2005) and a photon index of 5.2 +/- 1.0 (C-statistic=84.4 with 93 bins). With the power law fit, the average observed (unabsorbed) flux in the 0.3-10 keV energy range is of 8.0e-13 (1.9e-10) erg cm^-2 s^-1. This is an official product of the Swift-XRT Team.