Influence of thermohaline convection on diffusion-induced iron accumulation in A stars

TL;DR

This paper investigates how thermohaline convection affects iron accumulation caused by atomic diffusion in A stars, revealing that such convection significantly reduces iron buildup and impacts stellar models.

Contribution

It provides the first detailed analysis of thermohaline convection's role in moderating iron accumulation in A-F stars, incorporating this process into abundance variation computations.

Findings

Iron accumulation persists but is greatly reduced when thermohaline convection is included.

Thermohaline convection influences the internal structure and evolution of A-type stars.

Results impact understanding of stellar oscillations and abundance anomalies.

Abstract

Atomic diffusion may lead to heavy element accumulation inside stars in certain specific layers. Iron accumulation in the Z-bump opacity region has been invoked by several authors to quantitatively account for abundance anomalies observed in some stars, or to account for stellar oscillations through the induced $\kappa$-mechanism. These authors however never took into account the fact that such an accumulation creates an inverse $\mu$-gradient, unstable for thermohaline convection. Here, we present results for A-F stars, where abundance variations are computed with and without this process. We show that iron accumulation is still present when thermohaline convection is taken into account, but much reduced compared to when this physical process is neglected. The consequences of thermohaline convection for A-type stars as well as for other types of stars are presented