Primary Period-Luminosity-Relation Calibrators in the Milky Way: Cepheids and RR Lyrae Physical basis, Calibration, and Applications

TL;DR

This review discusses the calibration of period-luminosity relations for Cepheids and RR Lyrae stars using Gaia data, highlighting recent developments, challenges like reddening, and applications in distance measurement.

Contribution

It provides an updated overview of period-luminosity relations with new insights from Gaia DR3 and discusses the complexities of reddening correction methods.

Findings

Gaia DR3 data refines period-luminosity relations.

Reddening correction via Wesenheit indices is oversimplified.

Cepheids in open clusters offer valuable calibration data.

Abstract

In this invited review I discuss the calibration and applications of the period-luminosity relation of classical Cepheid and RR Lyrae stars. After a brief introduction, starting with results from Hipparcos and discussing some post-Hipparcos era developments, I focus on recent results using Gaia Data Release 3 data. I present an overview of the most recent period-luminosity relations, a discussion and some new results on Cepheids in open clusters. I also discuss the effect of reddening and that the use of Wesenheit indices is actually an oversimplification to dealing with the problem of reddening.