GCN Circular 10935
D. Grupe (PSU) reports on behalf of the Swift-XRT team: We have analyzed 6162 s of XRT data for GRB 100704A (Grupe et al. GCN Circ. 10929), from 92 s to 18.5 ks after the BAT trigger. The data comprise 317 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The X-ray light curve displays a strong flare starting at about 140s and peaking at 190s after the burst. As mentioned in GCN Circ. 10929, this flare coincides with a flare seen in the BAT. The rest of the light curve can be modeled with a series of power-law decays. After the flare the afterglow decays with a slope of 0.32 and breaks at about 1 ks after the burst followed by a decay slope of 0.76+/-0.06. A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.96 (+/-0.04). The best-fitting absorption column is 3.23 (+/-0.14) x 10^21 cm^-2, in excess of the Galactic value of 1.0 x 10^21 cm^-2 (Kalberla et al. 2005). With an excess absorption column density of 2.32 x 10^21 cm^-2 the NH-redshift relation by Grupe et al. (2007, AJ 133, 2216) suggests a redshift z<3.0. The PC mode spectrum has a photon index of 2.6 (+/-0.3) and a best-fitting absorption column of 3.1 (+0.9, -0.8) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.5 x 10^-11 (8.3 x 10^-11) erg cm^-2 count^-1. If the light curve continues to decay with a power-law decay index of 0.76, the count rate at T+24 hours will be 0.045 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.6 x 10^-12 (3.7 x 10^-12) erg cm^-2 s^-1 and 0.027 counts s^-1 T+48h. The UVOT-enhanced position of the afterglow has already been reported by Osborne et al. (GCN Circ. 10930). The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00426722. This circular is an official product of the Swift-XRT team.