Posterior probability distributions of the separation, ρ, position angle, θ, and planet-to-star flux contrast, δ, of β Pic b in L′ (left panel) and M′ (right panel). The marginalized 1D distributions of the parameters are shown in the diagonal panels and the marginalized 2D distributions are shown for all parameter pairs in the off-axis panels. The parameter values and uncertainties above the diagonal panels correspond to the median, and 16th and 84th percentiles of the samples (also indicated by the vertically dashed lines). Contours overlaid on the 2D distributions correspond to 1σ, 2σ, and 3σ confidence levels. The best-fit results from the Hessian minimization are shown with red symbols. See Sect. 4.3.3 for a derivation of the photometric error budget.