Gravitational settling of 22Ne and white dwarf evolution

Understand

We study the effects of the sedimentation of the trace element 22Ne in the cooling of white dwarfs.

• In contrast with previous studies, which adopted a simplified treatment of the effects of 22Ne sedimentation, this is done self-consistently for the first time, using an up-to-date stellar evolutionary code in which the diffusion equation is coupled with the full set of equations of stellar evolution.
• Due the large neutron excess of 22Ne, this isotope rapidly sediments in the interior of the white dwarf.
• Although we explore a wide range of parameters, we find that using the most reasonable assumptions concerning the diffusion coefficient and the physical state of the white dwarf interior the delay introduced by the ensuing chemical differentation is minor for a typical 0.6 Msun white dwarf.