Exploring the evolution of classical cepheids with MESA

Abstract

Classical Cepheid stars play an important role in the rst step of the distance ladder determination in the Milky Way and in nearby galaxies. The period-luminosity rela- tionship of classical Cepheid stars is used to calculate the Hubble constant which is a measurement of the expansion of the universe. Using Modules for Experiments in Stellar Astrophysics (MESA), new evolution models with and without convective core overshooting are used to probe for the period rate change at the di erent crossing of the instability strip. A population synthesis analysis shows that 63.4% of classical Cepheids have positive period rate change while the rest have negative period rate change. With overshooting, 91.1% of classical Cepheid stars have positive period rate change. To account for the di erence in the number of classical Cepheid stars that are observed versus those that are modeled with MESA, mass-loss, rotation and metallic- ity need to be added to the models to help explain the di erence with observations.