Radial Stellar Pulsation and Three-Dimensional Convection. IV. Full Amplitude Three-Dimensional Solutions

TL;DR

This paper presents three-dimensional hydrodynamic simulations of RR Lyrae stars, capturing convection and pulsation interactions without phenomenological models, and compares results with previous two-dimensional models to understand amplitude and light curve differences.

Contribution

It provides the first full amplitude 3D simulations of RR Lyrae stars, improving the modeling of convection-pulsation interactions over prior 2D approaches.

Findings

3D simulations produce similar light amplitudes to 2D models in the middle of the instability strip.

Differences in light curves are observed during decreasing light phases, due to numerical and physical factors.

The interaction between pulsation and convection in 3D is consistent with 2D results, with some variations near the edges of the instability strip.

Abstract

Three dimensional hydrodynamic simulations of full amplitude RR Lyrae stars have been computed for several models across the instability strip. The three dimensional nature of the calculations allows convection to be treated without reference to a phenomenological approach such as the local mixing length theory. Specifically, the time dependent interaction of the large scale eddies and the radial pulsation is controlled by the conservation laws, while the effects of smaller convective eddies are simulated by an eddy viscosity model. The light amplitudes for these calculations are quite similar to those of our previous two dimensional calculations in the middle of the instability strip, but somewhat lower near the red edge, the fundamental blue edge, and for the one first overtone model we computed. The time dependent interaction between the radial pulsation and the convective energy transport is essentially the same in three dimensions as it is in two dimensions. There are some differences between the light curves between the two and three dimensional simulations, particularly during decreasing light. Reasons for the differences, both numerical and physical are explored.