Best-fitting BPASS binary track for AB 6, calculated for M_i = 60 M_⊙, q_i = 0.7, and P_i = 16 d. The upper multi-colored track depicts the evolution of the WR primary until its core-collapse. The colors refer to surface hydrogen mass fractions of 0.45 < X_H < 0.7 (blue), 0.2 < X_H < 0.45 (red), 0.05 < X_H < 0.2 (orange), and X_H < 0.05 (green). The WC and RLOF phases are also marked. A track for a single 60 M_⊙ star is shown for comparison (dashed gray line). The lower track depicts the evolution track of the O-type companion until the core collapse of the primary.