On the Metallicity Dependence of Classical Cepheid Light Amplitudes

TL;DR

This study investigates how the light amplitudes of classical Cepheid variable stars depend on their metallicity, revealing that metal-poor Cepheids generally have smaller amplitudes than metal-rich ones, which impacts distance measurements.

Contribution

It provides empirical evidence of metallicity's effect on Cepheid amplitudes across multiple galaxies, challenging previous null or opposite dependence assumptions.

Findings

Metal-poor Cepheids have smaller V-band amplitudes.

Results offer a way to estimate metallicity from light amplitudes.

Findings can improve distance scale calibrations.

Abstract

Classical Cepheids remain a cornerstone of the cosmic distance scale, and thus characterizing the dependence of their light amplitude on metallicity is important. Period-amplitude diagrams constructed for longer-period classical Cepheids in IC 1613, NGC 3109, SMC, NGC 6822, LMC, and the Milky Way imply that very metal-poor Cepheids typically exhibit smaller V-band amplitudes than their metal-rich counterparts. The results provide an alternate interpretation relative to arguments for a null and converse metallicity dependence. The empirical results can be employed to check predictions from theoretical models, to approximate mean abundances for target populations hosting numerous long-period Cepheids, and to facilitate the identification of potentially blended or peculiar objects.