Bright single-mode RR Lyrae stars: matching Gaia EDR3 with pulsation and evolutionary models

TL;DR

This study combines observational data with models to accurately determine luminosities of RR Lyrae stars, validating Gaia EDR3 parallaxes and exploring discrepancies in a subset of stars.

Contribution

It presents a method integrating metallicity, magnitudes, and models to derive stellar luminosities and compares them with Gaia parallaxes, confirming model accuracy and identifying peculiar cases.

Findings

Excellent agreement between model-derived and Gaia parallaxes for most stars.

No parallax shift needed when using alpha-enhanced models.

Approximately 10% of stars show unexplained 'distance keeping' behavior.

Abstract

We combine observed metallicity, optical and infrared magnitudes with evolutionary and pulsation models to derive average luminosities for 156 single-mode RR Lyrae stars. These luminosities are compared with those obtained from the Gaia EDR3 parallaxes, and found in excellent agreement with the high accuracy subsample (62 stars, with relative parallax errors less than 2%). With the temperature and metallicity scale used, no parallax shift seems to be necessary when alpha-enhanced evolutionary models are employed. Some 10% of the sample shows curious `distance keeping' between the evolutionary and pulsation models. The cause of this behavior is not clear at this moment but can be cured by an excessive increase of the reddening.