Fe K line variability of PID 319, investigated for the four Chandra (open squares) and six XMM (filled circles) intervals. The emission line was modelled by a Gaussian, and the rest-frame line-centroid energy (upper panel), line width measured by the Gaussian dispersion (middle panel) and the normalization in units of 10^-7 photons s^-1 cm^-2. In the upper panel, the nominal line energy of 6.4 keV expected for cold Fe is indicated by a dotted line. The dashed vertical line indicates the ~6 year gap between the 2000−2002 and 2007−2010 periods.