Left panel: orbital period and eccentricity for binary star systems with evolved members, with period values normalized by the orbital period of a hypothetical companion that grazes the surface of each primary star, P_surface, assuming M₁ = 1.36 M_⊙ and M₂ = 0.5 M_⊙. The sharp transition from eccentric systems to almost all circular orbits at P/P_surface ≈ 10 is likely an outcome of tidal circularization. Right panel: normalized period and inferred radial velocity amplitude for the same systems.