Impact of the relativistic effects on the asorption features. Top: Absorption profiles for v₀ = 0.00, 0.10, 0.30c (colour coding, see legend) and N_H = 10²³, log(ξ₀) = 4 in the rest-frame spectrum between 6–10 keV. For increasing v₀, absorption lines are increasingly blueshifted and show lower EWs, as was expected from special relativity effects. Bottom: Ratio, Ψ_rel, between intrinsic and observed gas opacity as a function of the gas velocity, v (in units of c).