Effects of moderate abundance changes on the atmospheric structure and colours of Mira variables (Research Note)

TL;DR

This study investigates how moderate deviations from solar abundances influence the atmospheric structure and colours of Mira variables using dynamical models, revealing effects on stratification and infrared colours, especially near minimum phase.

Contribution

It introduces two new dynamical opacity-sampling models with varied abundances and compares their atmospheric and colour effects to a solar-abundance model, highlighting abundance impacts.

Findings

Abundance variations affect atmospheric stratification.

Infrared colours are influenced by abundance, especially near minimum phase.

Cycle-to-cycle differences often mask abundance effects.

Abstract

Aims. We study the effects of moderate deviations from solar abundances upon the atmospheric structure and colours of typical Mira variables. Methods. We present two model series of dynamical opacity-sampling models of Mira variables which have (1) 1 solar metallicity 3 and (2) "mild" S-type C/O abundance ratio ([C/O]=0.9) with typical Zr enhancement (solar +1.0). These series are compared to a previously studied solar-abundance series which has similar fundamental parameters (mass, luminosity, period, radius) that are close to those of o Cet. Results. Both series show noticeable effects of abundance upon stratifications and infrared colours but cycle-to-cycle differences mask these effects at most pulsation phases, with the exception of a narrow-water-filter colour near minimum phase.