Mixing and Overshooting in Surface Convection Zones of DA White Dwarfs: First Results from ANTARES

Abstract

We present results of a large, high resolution 3D hydrodynamical simulation of the surface layers of a DA white dwarf (WD) with $T_{\mathrm{eff}}=11800$ K and $\log (g)=8$ using the ANTARES code, the widest and deepest such simulation to date. Our simulations are in good agreement with previous calculations in the Schwarzschild-unstable region and in the overshooting region immediately beneath it. Farther below, in the wave-dominated region, we find that the rms horizontal velocities decay with depth more rapidly than the vertical ones. Since mixing requires both vertical and horizontal displacements, this could have consequences for the size of the region that is well mixed by convection, if this trend is found to hold for deeper layers. We discuss how the size of the mixed region affects the calculated settling times and inferred steady-state accretion rates for WDs with metals observed in their atmospheres.

This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review (author accepted manuscript). 13 pages, 14 figures

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