Eccentricity–period diagrams for various samples. The meaning of the various symbols is given in the upper right panel. (a) Mild barium stars; (b) strong barium stars; (c) mild (open squares) and strong (filled squares) barium stars plotted together. The dashed line corresponds to the upper envelope of the data points, well represented by the condition 143 R_⊙ = R_Roche = A (1 − e) [0.38 + 0.2log(M_Ba/M_WD)], corresponding to RLOF occurring at periastron for a star of radius 143 R_⊙. A is the semi-major axis of the orbit, linked to the orbital period P through the third Kepler law, adopting component masses of M_Ba = 2 M_⊙ and M_WD = 0.65 M_⊙; (d) S stars (triangles). The S star HD 184185, with P ∼ 15723 d and e ∼ 0, falls in the low e – long P gap (represented by the hatched area), probably as a consequence of its still-uncertain orbital parameters; (e) as in (c), adding CEMP-s and CH stars (blue 5-branch crosses; squared crosses correspond to carbon dwarfs from Jorissen et al. 2016a). The dwarf CEMP star HE 0024−2523 with an orbital period of 3.4 d falls outside the graph boundaries.