High-precision distance measurements with classical pulsating stars

TL;DR

This paper reviews the use of classical Cepheid and RR Lyrae stars as standard candles, discussing recent advances in calibrations, systematic uncertainties, and their role in high-precision cosmic distance measurements.

Contribution

It provides a comprehensive overview of recent theoretical and observational efforts to improve the calibration and application of classical pulsating stars for precise distance measurements.

Findings

Advances in multi-wavelength calibration of Cepheids and RR Lyrae.

Identification of key systematic uncertainties affecting distance estimates.

Outlook for future improvements with extremely large telescopes.

Abstract

Classical Cepheid and RR Lyrae variables are radially pulsating stars that trace young and old-age stellar populations, respectively. These classical pulsating stars are the most sensitive probes for the precision stellar astrophysics and the extragalactic distance measurements. Despite their extensive use as standard candles thanks to their well-defined Period-Luminosity relations, distance measurements based on these objects suffer from their absolute primary calibrations, metallicity effects, and other systematic uncertainties. Here, I present a review of classical Cepheid, RR Lyrae, and Type II Cepheid variables starting with a historical introduction and describing their basic evolutionary and pulsational properties. I will focus on recent theoretical and observational efforts to establish absolute scale for these standard candles at multiple wavelengths. The application of these classical pulsating stars to high-precision cosmic distance scale will be discussed along with observational systematics. I will summarize with an outlook for further improvements in our understanding of these classical pulsators in the upcoming era of extremely large telescopes.