Metallicities from high resolution spectra of 49 RR Lyrae Variables

TL;DR

This study provides precise metallicity measurements for 58 RR Lyrae stars using high-resolution spectra, enabling improved period-luminosity-metallicity relations in infrared bands, crucial for distance measurements.

Contribution

It offers new high-resolution spectroscopic metallicities for RR Lyrae stars and refines PLZ relationships in infrared and Wesenheit magnitudes, enhancing distance scale accuracy.

Findings

Metallicities measured with ~0.13 dex uncertainty.

New PLZ relations in WISE W1 and W2 bands.

Improved calibration for RR Lyrae distance measurements.

Abstract

Accurate metallicities of RR Lyrae are extremely important in constraining period-luminosity-metallicity relationships (PLZ), particularly in the near-infrared. We analyse 69 high-resolution spectra of Galactic RR Lyrae stars from the Southern African Large Telescope (SALT). We measure metallicities of 58 of these RR Lyrae stars with typical uncertainties of 0.13 dex. All but one RR Lyrae in this sample has accurate ({\sigma}_parallax ~ 10%) parallax from Gaia. Combining these new high resolution spectroscopic abundances with similar determinations from the literature for 93 stars, we present new PLZ relationships in WISE W1 and W2 magnitudes, and the Wesenheit magnitudes W(W1,V-W1) and W(W2,V-W2).