Pulsation Period Change & Classical Cepheids: Probing the Details of Stellar Evolution

TL;DR

This paper uses stellar evolution models and precise measurements of period changes in Galactic Cepheids Polaris and l Carinae to investigate their stellar evolution, mass loss, and implications for the period-luminosity relation.

Contribution

It combines observational data with models to analyze mass loss and evolution in Cepheids, providing new insights into their physical processes.

Findings

l Car has a mass of about 9 solar masses, consistent with pulsation models.

Polaris requires enhanced mass-loss rates to explain its period change.

Results inform understanding of Cepheid evolution and mass-loss mechanisms.

Abstract

Measurements of secular period change probe real-time stellar evolution of classical Cepheids making these measurements powerful constraints for stellar evolution models, especially when coupled with interferometric measurements. In this work, we present stellar evolution models and measured rates of period change for two Galactic Cepheids: Polaris and l Carinae, both important Cepheids for anchoring the Cepheid Leavitt law (period-luminosity relation). The combination of previously-measured parallaxes, interferometric angular diameters and rates of period change allows for predictions of Cepheid mass loss and stellar mass. Using the stellar evolution models, We find that l Car has a mass of about 9 $M_\odot$ consistent with stellar pulsation models, but is not undergoing enhanced stellar mass loss. Conversely, the rate of period change for Polaris requires including enhanced mass-loss rates. We discuss what these different results imply for Cepheid evolution and the mass-loss mechanism on the Cepheid instability strip.