New simulations of accreting DA white dwarfs: inferring accretion rates from the surface contamination

TL;DR

This paper presents a comprehensive grid of models for hydrogen-rich white dwarfs accreting heavy elements, incorporating thermohaline convection to accurately estimate accretion rates from surface contamination.

Contribution

It introduces a new set of evolutionary models that include thermohaline mixing, improving the accuracy of accretion rate estimations in white dwarfs with polluted atmospheres.

Findings

Provides a grid of models for different temperatures and hydrogen contents.

Includes thermohaline convection in the accretion process.

Offers reliable accretion rate estimates for white dwarfs.

Abstract

A non negligible fraction of white dwarf stars show the presence of heavy elements in their atmospheres. The most accepted explanation for this contamination is the accretion of material coming from tidally disrupted planetesimals, which form a debris disk around the star. We provide a grid of models for hydrogen rich white dwarfs accreting heavy material. We sweep a 3D parameter space involving different effective temperatures, envelope's hydrogen content and accretion rates. The grid is appropriate for determining accretion rates in white dwarfs showing the presence of heavy elements. Full evolutionary calculations of accreting white dwarfs were computed including all relevant physical processes, particularly the fingering (thermohaline) convection, a process neglected in most previous works, that has to be considered to obtain realistic estimations. Accretion is treated as a continuous process and bulk Earth composition is assumed for the accreted material. We obtain final (stationary or near stationary) and reliable abundances for a grid of models representing hydrogen rich white dwarfs of different effective temperatures and hydrogen contents, applied to various accretion rates. Our results provide estimates of accretion rates, accounting for thermohaline mixing, to be used for further studies on evolved planetary systems.