Top panel: photoionization phase plot showing the ionization solution for component 3 of epoch 2015b. We use the 2015 NGC 7469 SED and proto-solar metallicity. Solid lines and associated colored bands represent the locus of U_H, N_H models, which predict the measured N_ion, and their 1σ uncertainties, while the dashed line is the lower limit on the O VI column-density that permits the phase-space above it. The black dot is the best χ² solution and is surrounded by a 1σχ² black contour. Bottom panel: component 3 multi-epoch photoionization phase plot, using the same enhanced metallicity we used for component 1. Measurements are shown as solid lines, lower limits as dashed lines, and upper limits as dotted lines. The measurements and limits are colored according to epoch of observation. The colored bands envelop measurements and limits for the same ion. For clarity’s sake, we do not show the errors on individual measurements (which are shown in the top panel for the 2015b epoch and are representative to all epochs). The nominal solution that satisfies all the N_ion constraints for the 2015b epoch is shown by the black circle. In Sect. 4.3.2 we describe a 2-phase model for fitting the variability seen in component 3. We show the U_H and N_H positions of these phases (3a and 3b) for the 2010 and 2015 epochs with red and blue “X” symbols.