The smallest planetary drivers of white dwarf pollution

TL;DR

This study investigates the minimum planetary mass capable of polluting white dwarfs, revealing Luna-sized objects as significant perturbers, and highlights an unexplored mass range affecting pollution timing.

Contribution

It identifies Luna-mass objects as the smallest perturbers capable of white dwarf pollution through numerical simulations, expanding understanding of potential planetary influences.

Findings

Luna-mass objects can effectively pollute white dwarfs.

Pollution timing increases as perturber mass approaches Luna mass.

A large, unexplored mass range exists between Earth and Luna in white dwarf systems.

Abstract

Many potential mechanisms for delivering planetary debris to within a few Roche radii of white dwarfs rely on gravitational scattering events that feature perturbers which are giant planets or terrestrial planets. However, the population of these planets orbiting white dwarfs is still unknown, and for a substantial fraction of white dwarfs the largest planetary survivors of stellar evolution may be sub-terrestrial mass minor planets. Here, we attempt to identify the smallest mass perturbers that could pollute white dwarfs. Through computationally expensive numerical simulations of both unstable and stable configurations of minor planets, we find that this critical lower bound equals approximately one Luna mass. Further, we find that as this mass limit is approached from above, the typical cooling age at which white dwarf pollution occurs increases. Consequently, there is a two order-of-magnitude range of perturber masses between Earth and its moon that has remained largely unexplored in white dwarf pollution studies, despite the potential formation of thousands of such Luna-sized objects in these systems.