Cepheid Mass-loss and the Pulsation -- Evolutionary Mass Discrepancy

TL;DR

This paper examines the mass discrepancy in Cepheid variables, suggesting that internal mixing, rather than significant mass-loss, explains the difference between evolutionary and pulsation masses.

Contribution

It challenges the idea that non-canonical mass-loss explains the mass discrepancy, proposing internal mixing as a plausible alternative.

Findings

Evolutionary masses are 17±5% greater than pulsation masses.

Mild internal mixing can account for the mass discrepancy.

Mass-loss of about 20% is not necessary to explain the observations.

Abstract

I investigate the discrepancy between the evolution and pulsation masses for Cepheid variables. A number of recent works have proposed that non-canonical mass-loss can account for the mass discrepancy. This mass-loss would be such that a 5Mo star loses approximately 20% of its mass by arriving at the Cepheid instability strip; a 14Mo star, none. Such findings would pose a serious challenge to our understanding of mass-loss. I revisit these results in light of the Padova stellar evolutionary models and find evolutionary masses are ($17\pm5$)% greater than pulsation masses for Cepheids between 5<M/Mo<14. I find that mild internal mixing in the main-sequence progenitor of the Cepheid are able to account for this mass discrepancy.