Hot Jupiters Have Giant Companions: Evidence for Coplanar High-eccentricity Migration
Abstract
This study considers the characteristics of planetary systems with giant planets based on a population-level analysis of the California Legacy Survey planet catalog. We identified three characteristics common to hot Jupiters (HJs). First, while not all HJs have a detected outer giant planet companion ( $M\sin i=0.3\mbox{--}30\,{M}_{\mathrm{Jup}}$ ), such companions are ubiquitous when survey completeness corrections are applied for orbital periods out to 40,000 days. Giant-harboring systems without an HJ also host at least one outer giant planet companion per system. Second, the mass distributions of HJs and other giant planets are indistinguishable. However, within a planetary system that includes an HJ, the outer giant planet companions are at least 3× more massive than the inner HJs. Third, the eccentricity distribution of the outer companions in HJ systems (with an average model eccentricity of <e> = 0.34 ± 0.05) is different from the corresponding outer planets in planetary systems without HJs (<e> = 0.19 ± 0.02). We conclude that the existence of two gas giants, where the outermost planet has an eccentricity ≥0.2 and is 3× more massive, are key factors in the production of an HJ. Our simple model based on these factors predicts that ~10% of warm and cold Jupiter systems will by chance meet these assembly criteria, which is consistent with our measurement of a 16% ± 6% relative occurrence of HJ systems to all giant-harboring systems. We find that these three features favor coplanar high-eccentricity migration as the dominant mechanism for HJ formation.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 2023
- DOI:
- 10.3847/2041-8213/acfdab
- arXiv:
- arXiv:2310.01567
- Bibcode:
- 2023ApJ...956L..29Z
- Keywords:
-
- Exoplanet formation;
- Exoplanet migration;
- Exoplanets;
- Hot Jupiters;
- 492;
- 2205;
- 498;
- 753;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 11 pages, 5 Figures, Accepted for Publication in ApJL