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Cepheid masses derived from pulsations or binary dynamics are generally lowerthan those derived from stellar evolution models. Recent efforts have beendedicated to investigating the effects of abundances, mass loss, rotation,convection and overshooting prescriptions for modifying the evolution tracks toreduce or remove this Cepheid mass discrepancy. While these approaches arepromising, either alone or in combination, more work is required to distinguishbetween possible solutions. Here we investigate nuclear reaction rate andopacity modifications on Cepheid evolution using the MESA code. We discuss theeffects of opacity increases at envelope temperatures of 200,000-400,000 Kproposed to explain the pulsation properties of hybrid main-sequence betaCep/Slowly Pulsating B (SPB) variables which will evolve into Cepheids. We makeuse of the RSP nonlinear radial pulsation modeling capability in MESA tocalculate periods and radial velocity amplitudes of Galactic Cepheids V1334Cyg, Polaris, and delta Cep.

Investigating Opacity Modifications and Reaction Rate Uncertainties to Resolve the Cepheid Mass Discrepancy