White dwarf pollution by planets in stellar binaries

Understand

Approximately $0.2 \pm 0.2$ of white dwarfs (WDs) show signs of pollution by metals, which is likely due to the accretion of tidally disrupted planetary material.

• Models invoking planet-planet interactions after WD formation generally cannot explain pollution at cooling times of several Gyr.
• We consider a scenario in which a planet is perturbed by Lidov-Kozai oscillations induced by a binary companion and exacerbated by stellar mass loss, explaining pollution at long cooling times.
• Our computed accretion rates are consistent with observations assuming planetary masses between $\sim 0.01$ and $1\,M_\mathrm{Mars}$, although nongravitational effects may already be important for masses $\lesssim 0.3 \, M_\mathrm{Mars}$.