Incidence of the brightness model complexity on the system-parameter posterior probability distribution (PPD), using unipolar models. a), b) Marginal PPDs (68%- and 95%-confidence intervals) of and for two unipolar brightness models, respectively, with a fixed and large structure (Γ_SH,1) and with free-confinement structure (Γ₂). A comparison with Fig. 4a shows that is constrained closer to zero. The reason is that non-uniform brightness models enable the exploration of additional dimensions of the parameter space and, therefore, provide additional adequate combinations of the contributing factors to compensate an anomalous occultation. In particular, the uniform time offset is now mainly compensated by a non-uniform BD, rather than by as in conventional analysis. It shows also the evolution of the marginal PPD toward larger when using more complex brightness models – which enable more localized brightness structure. c), d) Marginal PPDs of ρ_⋆ and for, respectively, Γ_SH,1 and Γ₂. These show the impact of the brightness distribution on the retrieved system parameters (i.e., e-b-ρ_⋆-BD correlation); in particular, it outlines the possible overestimation of ρ_⋆ by 5% (i.e., at 6σ of the conventional estimate) when using extended brightness models, e.g., a uniform brightness distribution.