Self-consistent Nonlinear Classical Cepheid Pulsations during Stellar Evolution with MESA

Abstract We extend the time-dependent convection (TDC) treatment in MESA by introducing eddy-viscous dissipation. This software change brings MESA-TDC into closer alignment with the radial stellar pulsation (RSP) framework of the MESA-RSP module. We demonstrate that the inclusion of the eddy viscosity in hydrodynamic stellar models remains stable on evolutionary timescales. We then present the first self-consistent integration of large-amplitude, nonlinear classical Cepheid pulsations directly within a MESA-star evolutionary run, demonstrating that the TDC formalism implemented in MESA-star and the MESA-RSP module are physically identical. Starting from a 6 M ⊙ blue-loop stellar evolution model, we demonstrate evolving the entire stellar model through pulsations as well as pausing the evolution, excising the core, and remeshing the envelope to match the grid used by MESA-RSP . We compare the pulsation properties (e.g., period, light and radius curves, and growth rate) with a matched MESA-RSP run, and find reasonable agreement between the two modules. This unified approach eliminates the reliance on separate postprocessing workflows and enables fully coupled evolution–pulsation simulations. This approach enables future studies of stellar pulsations with the inclusion of composition gradients, mass loss, or rotation. It also enables future studies of the ϵ mechanism as well as providing a physical source of viscosity for other science cases explored using MESA ’s hydrodynamics solver. We have integrated these modifications into the MESA-star module, enabling open-source use by the community.