Characteristics of bright ab-type RR Lyrae stars from the ASAS and WASP surveys

TL;DR

This study analyzes high-precision light curves of 268 RR Lyrae stars from ASAS and WASP surveys, revealing differences in physical parameters related to the Blazhko effect, metallicity, and stellar environment, including the identification of a new metal-rich subgroup.

Contribution

It provides a comprehensive Fourier analysis of RR Lyrae stars from multiple surveys, compares their properties across different environments, and identifies a new group of metal-rich RR Lyrae stars.

Findings

Blazhko stars have lower amplitudes and longer rise times.

Star location in Fourier coefficient plots depends mainly on metallicity.

A new group of metal-rich, low-luminous RR Lyrae stars was identified.

Abstract

In this article, we present results based on high-density, high-precision Wide-Angle Search for Planets (WASP) light curves supplemented with lower-precision photometry from the All-Sky Automated Survey (ASAS) for 268 RR Lyrae stars (176 regular, 92 Blazhko). Light curves were Fourier-decomposed and coefficients from WASP were transformed to the ASAS standard using 24 common stars. Coefficients were then compared with similar data from Galactic globular clusters, the Galactic bulge and the Large and Small Magellanic Clouds (LMC and SMC). Using Fourier coefficients, we also calculated physical parameters via standard equations from the literature. We confirmed the results of previous authors, including lower amplitudes and longer rise times for Blazhko stars. It was found that in the $R_{31}$ vs. $R_{21}$ plot the location of a star depends mainly on its metallicity and that Blazhko stars prefer a different location than modulation-free stars. Field and globular-cluster RR Lyrae variables have a different $\phi_{21}$ and $\phi_{31}$ than stars in the LMC, SMC and in Galactic bulge. Although there are some weak indications that Blazhko stars could prefer a slightly lower metallicity and shorter periods, no convincing proof was found. The most interesting highlight is the identification of a very recently proposed new group of metal-rich RR Lyrae type stars. These low-luminous, metal-strong variables, which comprise both Blazhko and regular stars, have shorter periods and about a 180 K higher temperature at constant $(B-V)_{0}$ than the rest of the stars in the sample.