Best orbital solution for AB outer orbit for both uncertainty assumptions in the astrometry before 1991. In both panels the solid line corresponds to the best fit model and the shaded area to the 1σ region. The solid black lines correspond to the best orbital solution assuming small uncertainties (σ ∼ 0.02″) and the blue ones assume large uncertainties (σ ∼ 0.1″). The dots markers correspond to the RV measurement of systemic velocities from our orbital solutions and the one obtained from CO modelling.