A CLASSICAL CEPHEID IN A LARGE MAGELLANIC CLOUD ECLIPSING BINARY: EVIDENCE OF SHORTCOMINGS IN CURRENT STELLAR EVOLUTIONARY MODELS?

The recent discovery and analysis of a classical Cepheid in the well-detached, double-lined, eclipsing binary OGLE-LMC-CEP0227 has provided the first determination of the dynamical mass of a classical Cepheid variable to an unprecedented 1% accuracy. We show here that modern stellar evolution models, widely employed to study Galactic and extragalactic stellar systems, are able to match simultaneously the mass and radius (and effective temperature) of the two components with a single value for the age of the system, without any specific fine-tuning, assuming the typical metallicity of LMC Cepheids. Our conclusion is that there is no obvious discrepancy between dynamical and evolutionary masses for the Cepheid star in this system, contrary to previous claims of an overestimate of the Cepheid mass by stellar evolution theory.