Toward a resolution of the bump and beat Cepheid mass discrepancies

Abstract

The extant beat and bump Cepheid mass discrepancy problems are reexamined with the new opacities of Iglesias and Rogers. Compared to calculations with the Los Alamos opacities, the period ratios P1/P0 and P2/P0 are strongly reduced for any fixed stellar parameters (L, M, T(eff), X, Z) and exhibit a novel, large sensitivity to luminosity and to metallicity. For the beat Cepheids the P1/P0 period ratios now yield masses between 4 and 7 solar masses, in agreement with the other mass determinations. Nonlinear calculations still fail to give stable beat pulsations, however.