The Hydrogen Ionization Front-Stellar Photosphere Interaction and the Period-Color Relations of Variable Stars

TL;DR

This paper reviews evidence that Cepheid variable stars exhibit a nonlinear period-color relation with a break at 10 days, discussing implications for distance measurements and cosmology, and exploring potential physical causes.

Contribution

It provides a comprehensive review of the statistical evidence for nonlinearity in Cepheid relations and discusses possible physical mechanisms behind this phenomenon.

Findings

Evidence supports a break at 10 days in Cepheid period-color relation

Nonlinearity impacts extragalactic distance scale estimates

Potential physical mechanisms for nonlinearity are proposed

Abstract

Recent evidence has emerged that the Cepheid PL relation in the LMC is nonlinear in the sense that the existing data are more consistent with two lines of differing slope with a break at a period of 10 days. We review the statistical evidence for this, the implications for the extra-galactic distance scale and CMB independent estimations of Hubble's constant and briefly outline one possible physical mechanism which could cause this nonlinearity.