Critical periods below which one of the components fills its Roche lobe at either the tip of the RGB (P_RGB, 1, dashed line at the bottom of the figure) or at the tip of the AGB (P_AGB, 1, solid line at the top of the figure). The values R_RGB, tip and R_AGB, tip are computed from the STAREVOL outputs. Red curves have solar metallicity Z = 0.0134 and black curves have [Fe/H]= − 0.5 or Z = 0.0043. Various superimposed lines in a series correspond to various barium-star masses, M_Ba, which may be identified from the starting point of the curve. The critical period P_RGB, 2 can be read off the P_RGB, 1 curve at the corresponding M_Ba value, which determines the key value R_RGB, tip. Although P_RGB, 1 and P_RGB, 2 are not strictly equal, they are not different enough to warrant a specific P_RGB, 2 curve that would jeopardize the clarity of the figure.