Eating Planets for Lunch and Dinner: Signatures of Planet Consumption by Evolving Stars

TL;DR

This paper investigates how the ingestion of planets by evolving stars affects stellar properties, revealing observable signatures like luminosity changes and spin-up that can inform exoplanet studies.

Contribution

It provides a comprehensive analysis of the effects of planet consumption across various stellar stages, highlighting observable signatures and their implications for exoplanet demographics.

Findings

Planet consumption causes transient luminosity features lasting centuries to millennia.

Post-consumption stellar spins can reach break-up speeds.

Stellar mass loss and nebula shapes can result from planet ingestion.

Abstract

Exoplanets have been observed around stars at all stages of stellar evolution, in many cases orbiting in configurations that will eventually lead to the planets being engulfed or consumed by their host stars, such as Hot Jupiters or ultra-short period planets. Furthermore, objects such as polluted white dwarfs provide strong evidence that the consumption of planets by stars is a common phenomenon. This consumption causes several significant changes in the stellar properties, such as changes to the stellar spin, luminosity, chemical composition, or mass loss processes. Here, we explore this wide variety of effects for a comprehensive range of stellar and planetary masses and stages of stellar evolution, from the main sequence over red giants to the white dwarfs. We determine that planet consumption can cause transient luminosity features that last on the order of centuries to millennia, and that the post-consumption stellar spins can often reach break-up speeds. Furthermore, stellar moss loss can be caused by this spin-up, as well as through surface grazing interactions, leading to to the formation of unusual planetary nebula shapes or collimated stellar gas ejections. Our results highlight several observable stellar features by which the presence or previous existence of a planet around a given star can be deduced. This will provide future observational campaigns with the tools to better constrain exoplanet demographics, as well as planetary formation and evolution histories.