Exomoons as sources of white dwarf pollution

Abstract

Polluted white dwarfs offer a unique way to study the bulk compositions of exoplanetary material, but it is not always clear if this material originates from comets, asteroids, moons, or planets. We combine N-body simulations with an analytical model to assess the prevalence of extrasolar moons as white dwarf (WD) polluters. Using a sample of observed polluted white dwarfs we find that the extrapolated parent body masses of the polluters are often more consistent with those of many solar system moons, rather than solar-like asteroids. We provide a framework for estimating the fraction of white dwarfs currently undergoing observable moon accretion based on results from simulated white dwarf planetary and moon systems. Focusing on a three-planet white dwarf system of Super-Earth to Neptune-mass bodies, we find that we could expect about one percent of such systems to be currently undergoing moon accretions as opposed to asteroid accretion.