Metallicity estimates of Galactic Cepheids based on Walraven photometry

TL;DR

This paper develops new empirical and theoretical methods to estimate the metallicity of Galactic Cepheids using Walraven photometry, achieving high accuracy and covering a broad metallicity range.

Contribution

It introduces novel empirical and theoretical calibrations of photometric metallicity indices for Cepheids based on Walraven data, improving accuracy and applicability.

Findings

Empirical calibration achieves better than 0.2 dex accuracy.

Theoretical calibration achieves better than 0.1 dex accuracy.

Calibrations cover a broad metallicity range from -0.5 to +0.5 dex.

Abstract

We present new empirical and theoretical calibrations of two photometric metallicity indices based on Walraven photometry. The empirical calibration relies on a sample of 48 Cepheids for which iron abundances based on high resolution spectra are available in the literature. They cover a broad range in metal abundance (-0.5 < [Fe/H] < +0.5) and the intrinsic accuracy of the Metallicity Index Color (MIC) relations is better than 0.2 dex. The theoretical calibration relies on a homogeneous set of scaled-solar evolutionary tracks for intermediate-mass stars and on pulsation predictions concerning the topology of the instability strip. The metal content of the adopted evolutionary tracks ranges from Z=0.001 to Z=0.03 and the intrinsic accuracy of the MIC relations is better than 0.1 dex.