Convective Overshoot and Macroscopic Diffusion in Pure-Hydrogen Atmosphere White Dwarfs. (arXiv:1906.11252v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Cunningham_T/0/1/0/all/0/1">Tim Cunningham</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tremblay_P/0/1/0/all/0/1">Pier-Emmanuel Tremblay</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Freytag_B/0/1/0/all/0/1">Bernd Freytag</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ludwig_H/0/1/0/all/0/1">Hans-Günther Ludwig</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Koester_D/0/1/0/all/0/1">Detlev Koester</a>
We present a theoretical description of macroscopic diffusion caused by
convective overshoot in pure-hydrogen DA white dwarfs using three-dimensional
(3D), closed-bottom, radiation hydrodynamics CO$^5$BOLD simulations. We rely on
a new grid of deep 3D white dwarf models in the temperature range 11400 K $leq
T_{mathrm{eff}} leq$ 18000 K where tracer particles and a tracer density are
used to derive macroscopic diffusion coefficients driven by convective
overshoot. These diffusion coefficients are compared to microscopic diffusion
coefficients from one-dimensional structures. We find that the mass of the
fully mixed region is likely to increase by up to 2.5 orders of magnitude while
inferred accretion rates increase by a more moderate order of magnitude. We
present evidence that an increase in settling time of up to 2 orders of
magnitude is to be expected which is of significance for time-variability
studies of polluted white dwarfs. Our grid also provides the most robust
constraint on the onset of convective instabilities in DA white dwarfs to be in
the effective temperature range from 18000 to 18250 K.
We present a theoretical description of macroscopic diffusion caused by
convective overshoot in pure-hydrogen DA white dwarfs using three-dimensional
(3D), closed-bottom, radiation hydrodynamics CO$^5$BOLD simulations. We rely on
a new grid of deep 3D white dwarf models in the temperature range 11400 K $leq
T_{mathrm{eff}} leq$ 18000 K where tracer particles and a tracer density are
used to derive macroscopic diffusion coefficients driven by convective
overshoot. These diffusion coefficients are compared to microscopic diffusion
coefficients from one-dimensional structures. We find that the mass of the
fully mixed region is likely to increase by up to 2.5 orders of magnitude while
inferred accretion rates increase by a more moderate order of magnitude. We
present evidence that an increase in settling time of up to 2 orders of
magnitude is to be expected which is of significance for time-variability
studies of polluted white dwarfs. Our grid also provides the most robust
constraint on the onset of convective instabilities in DA white dwarfs to be in
the effective temperature range from 18000 to 18250 K.
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