White Dwarf Pollution by Asteroids from Secular Resonances

TL;DR

This paper explores how secular resonances in evolving planetary systems can excite asteroids' eccentricities, leading to their tidal disruption and continuous metal pollution in white dwarf atmospheres, supported by analytic and simulation models.

Contribution

It demonstrates that secular resonances driven by outer companions can cause asteroid disruption, offering a new explanation for white dwarf pollution across various planetary architectures.

Findings

Secular resonances can induce asteroid eccentricities leading to tidal disruption.

Planetary system evolution shifts resonance locations, affecting asteroid dynamics.

Resonance-driven pollution is viable in diverse exoplanetary systems.

Abstract

In the past few decades, observations have revealed signatures of metals polluting the atmospheres of white dwarfs. The diffusion timescale for metals to sink from the atmosphere of a white dwarf is of the order of days for a hydrogen-dominated atmosphere. Thus, there must be a continuous supply of metal-rich material accreting onto these white dwarfs. We investigate the role of secular resonances that excite the eccentricity of asteroids allowing them to reach star-grazing orbits leading them to tidal disruption and the formation of a debris disc. Changes in the planetary system during the evolution of the star lead to a change in the location of secular resonances. In our Solar System, the engulfment of the Earth will cause the $\nu_6$ resonance to shift outwards which will force previously stable asteroids to undergo secular resonant perturbations. With analytic models and $N$--body simulations we show that secular resonances driven by two outer companions can provide a source of continuous pollution. Secular resonances are a viable mechanism for the pollution of white dwarfs in a variety of exoplanetary system architectures.