Nonlinear simulations of the convection-pulsation coupling

TL;DR

This paper presents two-dimensional direct simulations of convection-pulsation coupling in Cepheids, revealing how convective motions can suppress stellar pulsations and assessing the limitations of traditional 1-D models.

Contribution

It introduces 2D DNS of convection-pulsation coupling in Cepheids, providing insights into nonlinear interactions and evaluating the accuracy of existing 1-D TDC models.

Findings

Convective motions can quench radial pulsations in Cepheids.

2D DNS can test and improve 1-D TDC models.

Simulations identify regimes where pulsations are suppressed.

Abstract

In cold Cepheids close to the red edge of the classical instability strip, a strong coupling between the stellar pulsations and the surface convective motions occurs. This coupling is by now poorly described by 1-D models of convection, the so-called "time-dependent convection models" (TDC). The intrinsic weakness of such models comes from the large number of unconstrained free parameters entering in the description of turbulent convection. A way to overcome these limits is to compute two-dimensional direct simulations (DNS), in which all the nonlinearities are correctly solved. Two-dimensional DNS of the convection-pulsation coupling are presented here. In an appropriate parameter regime, convective motions can actually quench the radial pulsations of the star, as suspected in Cepheids close to the red edge of the instability strip. These nonlinear simulations can also be used to determine the limits and the relevance of the TDC models.