GCN Circular 10313
K.L. Page (U. Leicester) and W.H. Baumgartner (GSFC/UMBC) report on behalf of the Swift-XRT team: We have analysed 8 ks of XRT data for the INTEGRAL GRB 100103A (Gotz et al. GCN Circ. 10307) obtained during two observations, from 3.3-10.3 ks and 196-224 ks after the trigger. The source found by Kennea & Baumgartner (GCN Circ. 10308; improved position given by Page et al. in GCN Circ. 10312) is now clearly fading, with a decay slope of alpha = 0.87 (+0.14, -0.10). We therefore confirm that this is, indeed, the X-ray afterglow. A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.86 (+0.32, -0.30). The best-fitting absorption column is 6.5 (+1.3, -0.7) x 10^21 cm^-2, in excess of the Galactic value of 2.4 x 10^21 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.9 x 10^-11 (1.7 x 10^-10) erg cm^-2 count^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00020125. This circular is an official product of the Swift-XRT team.