Determination of the iron content of Cepheids from the shape of their light curves

TL;DR

This study establishes a method to estimate the iron content of Cepheid variable stars using their light curve shapes, enabling metallicity measurements for stars too faint for spectroscopy.

Contribution

It introduces empirical relations between Fourier light curve parameters and iron abundance, allowing photometric metallicity estimation for classical Cepheids.

Findings

Photometric [Fe/H] can be determined with 0.15 dex accuracy.

Method works for stars without prior spectroscopic data.

Metallicity relations are consistent across Galactic and Magellanic Cloud Cepheids.

Abstract

We present the study of the metallicity dependence of the Fourier amplitude ratios R_21 and R_31 for the light curves of short-period Galactic classical Cepheids in B, V, R_C and I_C bands. Based on the available photometric and spectroscopic data we determined the relations between the atmospheric iron abundance, [Fe/H], and the Fourier parameters. Using these relations we calculated the photometric [Fe/H] values of all program Cepheids with an average accuracy of 0.15 dex. No spectroscopic iron abundance was known before for 14 of these stars. These empirical results provide an alternate method to determine the iron abundance of classical Cepheids too faint for spectroscopic observations. We also checked whether the metal-poor Cepheids of both Magellanic Clouds follow the same relationships, and a good agreement was found.