Time evolution of the osculating orbital elements over a time span − 11 000 to + 1000 days from the epoch T₀ = 2 456 224.724705, covered by observations of ξ Tau. Left: the semi-major axis a₁, eccentricity e₁, inclination i₁, longitude of ascending node Ω₁, and the argument of pericentre ω₁ (poorly defined because e₁ → 0) of the inner, eclipsing binary orbit (components Aa and Ab). Right: the same parameters a₂,e₂,i₂,Ω₂,ω₂ for orbit 2 (i.e. components (Aa+Ab) and B). All these plots correspond to the simulation with χ² = 2578, presented in Fig. 9. Variations in the inclination i₁ and argument of pericentre ω₂ are of major interest, since they result in observable effects. On the other hand, the distant orbit 3 (not shown here) exhibits only minor variations of its elements. The bump in the osculation elements of orbit 2 at JD ≈ 2 455 500 is related to the passage of component C through its pericentre.