Top panels: values of l(l + 1) of unstable non-radial l = 1−4 modes for two coeval models of the components of β Cen, 12.0-M_⊙ model #110 for the primary with V_rot = 226 km s^-1 and f_rot = 0.56227 d^-1 (left) and 10.6-M_⊙ model #79 for the secondary with V_rot = 94 km s^-1 and f_rot = 0.31746 d^-1 (right), plotted as a function of frequency in the inertial frame of reference. Bottom panels: separation parameters, λ, of unstable modes for the same two models of primary (left) and secondary (right). The models were calculated with OP opacities for X = 0.7374 and Z = 0.0134. In all panels vertical dashed lines indicate the observed frequencies, the short-dashed line is the combination term f₁.