Making systems of Super Earths by inward migration of planetary embryos

TL;DR

This paper demonstrates through N-body simulations that inward migration of planetary embryos in radiative disks can naturally form compact systems of hot super Earths, resembling observed systems like Kepler 11.

Contribution

It reveals that weak corotation torque and sustained eccentricities in multi-embryo systems favor inward migration, leading to super Earth formation near the disk's inner edge.

Findings

Inward migration is dominant for embryos less than 4 Earth masses.

Multi-embryo interactions sustain eccentricities that dampen outward migration.

Formed super Earths are in resonant chains near the disk's inner edge.

Abstract

Using N-body simulations with planet-disk interactions, we present a mechanism capable of forming compact systems of hot super Earths such as Kepler 11. Recent studies show that outward migration is common in the inner parts of radiative disks. However we show that two processes naturally tip the balance in favor of inward migration. First the corotation torque is too weak to generate outward migration for planetary embryos less massive than $4\mearth$. Second, system of multiple embryos generate sustained non-zero eccentricities that damp the corotation torque and again favor inward migration. Migration and accretion of planetary embryos in realistic disks naturally produce super Earths in resonant chains near the disk inner edge. Their compact configuration is similar to the observed systems.