The Orbital Evolution of Gas Giant Planets around Giant Stars

TL;DR

This paper models the orbital evolution of gas giant planets around giant stars, showing how stellar evolution influences planetary engulfment and explaining observed distributions around massive stars.

Contribution

It provides a detailed calculation of planetary orbital changes during stellar evolution, highlighting the role of tidal interactions in planet engulfment around evolved stars.

Findings

Close-in planets are often engulfed by giant stars due to tidal interactions.

Engulfment efficiency increases with planetary mass and decreases with stellar mass.

Results explain the scarcity of close-in planets around evolved stars more massive than 1.5 Msun.

Abstract

Recent surveys have revealed a lack of close-in planets around evolved stars more massive than 1.2 Msun. Such planets are common around solar-mass stars. We have calculated the orbital evolution of planets around stars with a range of initial masses, and have shown how planetary orbits are affected by the evolution of the stars all the way to the tip of the Red Giant Branch (RGB). We find that tidal interaction can lead to the engulfment of close-in planets by evolved stars. The engulfment is more efficient for more-massive planets and less-massive stars. These results may explain the observed semi-major axis distribution of planets around evolved stars with masses larger than 1.5 Msun. Our results also suggest that massive planets may form more efficiently around intermediate-mass stars.