Top: photoionization phase plot showing the constraints for component 1 of epoch 2015b, where 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; dashed lines represent N_ion lower limits that permit a solution in the phase-space above them; and dotted lines represent N_ion upper limits that permit a solution in the phase-space below the line. Since the CNO lower limit bands do not intersect with the H I band, it is clear that there is no viable photoionization solution for this case. Middle: same N_ion constraints and same SED as in the top panel, but assuming super-solar metallicity as described in Sect. 4.1.1. The viable physical solution and its 1-σ error are shown by the black dot and surrounding black oval, respectively. Bottom: phase plot showing the photoionization constraints for component 1 in three different epochs, using the same SED and abundances used in the middle panel. Similar presentation to the other panels, where for clarity’s sake we do not show the errors on individual measurements, (the errors are similar to the ones shown in the middle panel). Most of the C IV, N V and Lyα constraints are lower limits. To help distinguish between them, we assign different length dashed lines for these lower limit constraints. The region between the three C IV constraints is shaded to help guide the eye. The “X” symbols show the location of the derived photoionization solutions for the different epochs where N_H is kept constant and the difference in U_H is equal to the difference in the measured UV flux for each epoch.