In Situ Formation and Dynamical Evolution of Hot Jupiter Systems

TL;DR

This paper proposes that many hot Jupiters form in situ through rapid gas accretion by Super-Earths, challenging the traditional migration theory, and predicts accompanying low-mass planets with specific dynamical features.

Contribution

It introduces a new in situ formation model for hot Jupiters via core accretion in the inner disk regions, with testable observational predictions.

Findings

Hot Jupiters can form in situ via rapid gas accretion by Super-Earths.

In situ formation predicts hot Jupiters are often accompanied by close-in low-mass planets.

Dynamical interactions can increase inclinations, making transits rare for these companions.

Abstract

Hot Jupiters, giant extrasolar planets with orbital periods shorter than ~10 days, have long been thought to form at large radial distances, only to subsequently experience long-range inward migration. Here, we propose that in contrast with this picture, a substantial fraction of the hot Jupiter population formed in situ via the core accretion process. We show that under conditions appropriate to the inner regions of protoplanetary disks, rapid gas accretion can be initiated by Super-Earth type planets, comprising 10-20 Earth masses of refractory composition material. An in situ formation scenario leads to testable consequences, including the expectation that hot Jupiters should frequently be accompanied by additional low-mass planets with periods shorter than ~100 days. Our calculations further demonstrate that dynamical interactions during the early stages of planetary systems' lifetimes should increase the inclinations of such companions, rendering transits rare. High-precision radial velocity monitoring provides the best prospect for their detection.