Accretion of Planetary Material onto Host Stars

TL;DR

This paper reviews how planetary material accretes onto host stars throughout their life cycle, discussing theoretical models, observational evidence, and different phases of stellar evolution.

Contribution

It provides a comprehensive overview of planetary accretion processes across stellar evolution stages, integrating models and observational data.

Findings

Tidal interactions can cause orbital decay and planetary engulfment.

White dwarfs show evidence of active planetary material accretion.

Limited chemical evidence for pollution in main sequence and red giant stars.

Abstract

Accretion of planetary material onto host stars may occur throughout a star's life. Especially prone to accretion, extrasolar planets in short-period orbits, while relatively rare, constitute a significant fraction of the known population, and these planets are subject to dynamical and atmospheric influences that can drive significant mass loss. Theoretical models frame expectations regarding the rates and extent of this planetary accretion. For instance, tidal interactions between planets and stars may drive complete orbital decay during the main sequence. Many planets that survive their stars' main sequence lifetime will still be engulfed when the host stars become red giant stars. There is some observational evidence supporting these predictions, such as a dearth of close-in planets around fast stellar rotators, which is consistent with tidal spin-up and planet accretion. There remains no clear chemical evidence for pollution of the atmospheres of main sequence or red giant stars by planetary materials, but a wealth of evidence points to active accretion by white dwarfs. In this article, we review the current understanding of accretion of planetary material, from the pre- to the post-main sequence and beyond. The review begins with the astrophysical framework for that process and then considers accretion during various phases of a host star's life, during which the details of accretion vary, and the observational evidence for accretion during these phases.