The accretion of migrating giant planets

TL;DR

This study investigates how the concurrent processes of giant planet accretion and migration influence each other, revealing that faster migrating planets accrete more gas and that gas crossing the gap varies with migration rate, challenging classical models.

Contribution

It presents a combined model of planet growth and migration, showing their mutual influence and the conditions under which gas crosses the planetary gap, which differs from traditional theories.

Findings

Fast migrating planets accrete more gas.

Gas predominantly originates from the inner disk for fast migration.

Gas crossing the gap varies with migration rate.

Abstract

Most studies concerning the growth and evolution of massive planets focus either on their accretion or their migration only. In this work we study both processes concurrently to investigate how they might mutually affect each other. We modeled a 2-dimensional disk with a steady accretion flow onto the central star and embed a Jupiter mass planet at 5.2 au. The disk is locally isothermal and viscosity is modeled using a constant $\alpha$. The planet is held on a fixed orbit for a few hundred orbits to allow the disk to adapt and carve a gap. After this period, the planet is released and free to move according to the gravitational interaction with the gas disk. The mass accretion onto the planet is modeled by removing a fraction of gas from the inner Hill sphere, and the removed mass and momentum can be added to the planet. Our results show that a fast migrating planet is able to accrete more gas than a slower migrating planet. Utilizing a tracer fluid we analyzed the origin of the accreted gas which comes predominantly originating from the inner disk for a fast migrating planet. In case of slower migration the fraction of gas from the outer disk increases. We also found that even for very high accretion rates in some cases gas crosses the planetary gap from the inner to the outer disk. Our simulations show that the crossing of gas changes during the migration process as the migration rate slows down. Therefore classical type II migration where the planet migrates with the viscous drift rate and no gas crosses the gap is no general process but may only occur for special parameters and at a certain time during the orbital evolution of the planet.