Left panel: predicted columns for the ions of Si and S for a spherical cloud with N_H = 10²² cm⁻² that is irradiated by a X-ray source with the spectrum defined by Fig. 12. Right panel: lines of constant ion column density color-coded for each different ion of Si (panels a and b) and S (panels c and d), for XSTAR simulated values of equivalent hydrogen column density, N_H, and ionization parameter, logξ. The assumed ion columns are the values measured during the strong dip of observation 8525 (Table 5). If a simple XSTAR model described the observation, we would expect these lines to cross in one point (within their error bars). The left column of the figure shows calculations without the effect of the optical companion (OC); the right column includes the UV radiation from the companion.