MCMC simulation for the model with χ² = 6695 (from Table 2). Distributions of all parameters, corresponding to local uncertainties, and correlations of all pairs of parameters is plotted as a standard ‘corner’. The order of 22 parameters is as follows (↓, →): m_sum, q₁, P₁, log e₁, i₁, Ω₁, ϖ₁, λ₁, R₁, R₂, P_rot1, ∆t₁, С_20,1, l_pole1, b_pole1, ϕ₀₁, A_w1, A_w2, B₀, h, g, and . The mean value is seen in the respective histogram. The number of walkers was set to 64. The whole chain contained 2400 samples, the burn-in phase took up to 1000 of them. In the course of iterations, walkers may drift away from the initial local minimum, because walkers perform also low-probability steps to higher χ² values, which may sometimes result in systematic shifts of (some of) the parameters. In this case, the MCMC was also affected by a change in the weights (w_sky = 10, w_ao = 0.1), which prevents the MCMC from fitting the systematics on the light curve at expense of the PISCO astrometric dataset.