Tidal Disruption of Planetesimals from an Eccentric Debris Disk Following a White Dwarf Natal Kick

TL;DR

This study uses N-body simulations to show that natal kicks in white dwarfs can create eccentric debris disks, leading to increased tidal disruptions of planetesimals and explaining observed pollution in white dwarf atmospheres.

Contribution

It demonstrates how white dwarf natal kicks can form eccentric debris disks and drive tidal disruption events, providing a new explanation for white dwarf pollution.

Findings

Eccentric debris disks form at 30-240 AU after natal kicks.

Approximately 80% of disks show apsidal alignment and counter-rotation.

Kick-induced disruptions match observed accretion rates over 100 Myr.

Abstract

The surfaces of many white dwarfs are polluted by metals, implying a recent accretion event. The tidal disruption of planetesimals is a viable source of white dwarf pollution and offers a unique window into the composition of exoplanet systems. The question of how planetary material enters the tidal disruption radius of the white dwarf is currently unresolved. Using a series of $N$-body simulations, we explore the response of the surrounding planetesimal debris disk as the white dwarf receives a natal kick caused by anisotropic mass loss on the asymptotic giant branch. We find that the kick can form an apse-aligned, eccentric debris disk in the range 30 to 240 AU which corresponds to the orbits of Neptune, the Kuiper Belt, and the scattered disk in our solar system. In addition, many planetesimals beyond 240 AU flip to counter-rotating orbits. Assuming an isotropic distribution of kicks, we predict that approximately 80% of white dwarf debris disks should exhibit significant apsidal alignment and fraction of counter-rotating orbits. The eccentric disk is able to efficiently and continuously torque planetesimals onto radial, star-grazing orbits. We show that the kick causes both an initial burst in tidal disruption events as well as an extended period of 100 Myr where tidal disruption rates are consistent with observed mass accretion rates on polluted white dwarfs.