On the Fate of Unstable Circumbinary Planets: Tatooine's Close Encounters with a Death Star

TL;DR

This paper investigates the fate of unstable circumbinary planets, quantifying how often they are ejected, captured, or accreted, and examines the potential observational signatures of tidal interactions during close encounters.

Contribution

It provides a detailed analysis of the outcomes of unstable circumbinary planets and assesses the likelihood of free-floating planets resulting from these processes.

Findings

80% of unstable planets are ejected from the system.

Approximately 20% of unstable planets collide with a star.

Tidal stripping during close passages is weak but may alter observable structures.

Abstract

Circumbinary planets whose orbits become unstable may be ejected, accreted, or even captured by one of the stars. We quantify the relative rates of these channels, for a binary of secondary star's mass fraction 0.1 with an orbit of 1AU. The most common outcome is ejection, which happens ~80% of the time. If binary systems form circumbinary planets readily and sloppily, this process may fill the Milky Way with free-floating planets. A significant fraction of the time, ~20%, the unstable planet strikes the primary or secondary. We tracked whether a Jupiter-like planet would undergo tidal stripping events during close passages, and find that these events are not strong enough to change the trajectory of the planet, though this may be observable from a changed structured for free-floating planets that are produced by this process.