Measured column densities, N_i, of individual elements as a function of orbital phase. Left: H- and He-like line series (circles) and Fe lines (crosses). Only measurements with relative uncertainties <75% are included. Right: column densities of the four most prominent ions, Ne x (circles), Mg xii (diamonds), Mg xi (squares), and Si xiv (triangles). Filled datapoints correspond to symmetric lines (see Fig. 12 and related discussions).