New homogeneous iron abundances of double-mode Cepheids from high-resolution echelle spectroscopy

TL;DR

This study accurately measures the metallicities of 17 double-mode Cepheids using high-resolution spectroscopy, revealing a strong correlation between their period ratios and metallicity, which enhances understanding of pulsation-metallicity relationships.

Contribution

It provides the first homogeneous, high-precision metallicity measurements for double-mode Cepheids and establishes a detailed period ratio--metallicity relation.

Findings

All Cepheids have solar or slightly subsolar metallicity.

Strong correlation between period ratio and metallicity.

Derived period ratio--metallicity relation improves pulsation models.

Abstract

Aims: We define the relationship between the double-mode pulsation of Cepheids and metallicity in a more accurate way, determine the empirical metallicities of double-mode Cepheids from homogeneous, high-resolution spectroscopic data, and study of the period-ratio -- metallicity dependence. Methods: The high S/N echelle spectra obtained with the FEROS spectrograph were analyzed using a self-developed IRAF script, and the iron abundances were determined by comparing with synthetic spectra assuming LTE. Results: Accurate [Fe/H] values of 17 galactic beat Cepheids were determined. All these stars have solar or slightly subsolar metallicity. Their period ratio P1/P0 shows strong correlation with their derived [Fe/H] values. The corresponding period ratio -- metallicity relation has been evaluated.