BBH model C0–C9 characterized by R_{C0 − C9} = 0.3 mas. Component C6 is ejected from core C0: the functions χ²(i_o). The curves χ²(i_o) obtained for different values of the mass ratios M_C0/M_C9 = 0.1, 0.5 and 0.8. All the curves are concave and show a minimum, but the solution corresponding to M_C0/M_C9 = 0.8 is not stable because the corresponding ratio (R_disk, C0/D_{L1 − C0})(i_o) is higher than 1 (see Fig. B.5). For solutions with M_C0/M_C9 ≤ 0.5 the solution with M_C0/M_C9 ≈ 0.5 has the smallest , i.e., the solution that provides the best fit of the VLBI component C6 corresponds to the BBH system C0–C9 characterized by R_{C0 − C9} ≈ 0.3 mas and M_C0/M_C9 ≈ 0.5.