Short-term stability of particles in the WD J0914+1914 white dwarf planetary system

TL;DR

This study investigates the stability and potential for rocky debris pollution in the unique white dwarf WD J0914+1914 system, focusing on the influence of a giant planet and gas disc through numerical simulations.

Contribution

It combines plausible planetary orbits and masses with numerical integrations to identify the gas disc's outer boundary and assess rocky debris pollution likelihood.

Findings

A highly inflated planet on a near-circular orbit fits current observations.

Rocky metal pollution signatures are limited to high-eccentricity particle trajectories.

The gas disc boundary depends on the planet's mass and orbit.

Abstract

Nearly all known white dwarf planetary systems contain detectable rocky debris in the stellar photosphere. A glaring exception is the young and still evolving white dwarf WD J0914+1914, which instead harbours a giant planet and a disc of pure gas. The stability boundaries of this disc and the future prospects for this white dwarf to be polluted with rocks depend upon the mass and orbit of the planet, which are only weakly constrained. Here we combine an ensemble of plausible planet orbits and masses to determine where observers should currently expect to find the outer boundary of the gas disc. We do so by performing a sweep of the entire plausible phase space with short-term numerical integrations. We also demonstrate that particle-star collisional trajectories, which would lead to the (unseen) signature of rocky metal pollution, occupy only a small fraction of the phase space, mostly limited to particle eccentricities above 0.75. Our analysis reveals that a highly inflated planet on a near-circular orbit is the type of planet which is most consistent with the current observations.