Successive common envelope events from multiple planets

TL;DR

This paper proposes a model for multiple common envelope events caused by successive engulfment of planets in evolving stars, potentially explaining observed planetary systems like WD 1856 b.

Contribution

It introduces a simplified model for multi-planet common envelope events and explores their implications for stellar and planetary evolution.

Findings

Model can explain the formation of planet WD 1856 b

Multiple CE events can occur in multi-planet systems

Impacts on understanding of stellar and planetary evolution

Abstract

Many stars harbour multi-planet systems. As these stars expand late in their evolutions, the innermost planet may be engulfed, leading to a common envelope (CE) event. Even if this is insufficient to eject the envelope, it may expand the star further, causing additional CE events, with the last one unbinding what remains of the envelope. This multi-planet CE scenario may have broad implications for stellar and planetary evolution across a range of systems. We develop a simplified version and show that it may be able to explain the recently observed planet WD 1856 b.