Partial Disruption of a Planet around a White Dwarf: The Effect of Perturbations from the Remnant Planet on the Accretion

Abstract

About 25%–50% of white dwarfs (WDs) are found to be polluted by heavy elements. It has been argued that the pollution could be caused by the tidal disruption of an approaching planet around the WD, during which a large number of clumps would be produced and would finally fall onto the WD. The reason that the planet approaches the WD is usually believed to be due to gravitational perturbations from another distant planet or stellar companion. However, the dynamics of the perturbations and the detailed partial disruption process are still poorly understood. In this study, we present an in-depth investigation of these issues. A triple system composed of a WD, an inner orbit planet, and an outer orbit planet is considered. The inner planet would be partially disrupted periodically over its long-term evolution. Fragments generated in the process are affected by gravitational perturbations from the remnant planet, facilitating their fall toward the WD. The mass-loss rate of the inner planet depends on both its internal structure and also on the orbital configuration of the planetary system.

Keywords

• White dwarf stars
• Exoplanets
• Dynamical evolution
• Tidal disruption