Dipole low-order g mode instability of metal-poor low-mass main-sequence stars due to the $\varepsilon$-mechanism

TL;DR

This study investigates the vibrational stability of metal-poor low-mass main-sequence stars, revealing that certain g-modes become unstable due to the $\varepsilon$-mechanism, especially at very low metallicities, with implications for stellar oscillations.

Contribution

The paper demonstrates that the $\varepsilon$-mechanism induces instability in dipole g-modes in metal-poor stars, extending the known instability range to higher masses at lower metallicities.

Findings

Dipole g$_1$- and g$_2$-modes become unstable for $Z\\la 6\times 10^{-4}$.

Instability extends to higher mass as metallicity decreases.

Outer convection zones are limited, reducing uncertainty in the analysis.

Abstract

We analyzed vibrational stability of metal-poor low-mass main-sequence stars due to the $\varepsilon$-mechanism. Since outer convection zones of the metal-poor stars is limited only to the very outer layers, the uncertainty in treatment of convection does not affect the result significantly. We found that the dipole g$_1$- and g$_2$-modes certainly become unstable due to the $\varepsilon$-mechanism for $Z\la 6\times 10^{-4}$. Besides that, we found that as the metallicity decreases the mass range of the $\varepsilon$-mechanism instability extends toward higher mass.