Warm Jupiters Need Close "Friends" for High-Eccentricity Migration -- A Stringent Upper Limit on the Perturber's Separation

Understand

We propose a stringent observational test on the formation of warm Jupiters (gas-giant planets with 10 d <~ P <~ 100 d) by high-eccentricity (high-e) migration mechanisms.

• Unlike hot Jupiters, the majority of observed warm Jupiters have pericenter distances too large to allow efficient tidal dissipation to induce migration.
• To access the close pericenter required for migration during a Kozai-Lidov cycle, they must be accompanied by a strong enough perturber to overcome the precession caused by General Relativity (GR), placing a strong upper limit on the perturber's separation.
• For a warm Jupiter at a ~ 0.2 AU, a Jupiter-mass (solar-mass) perturber is required to be <~ 3 AU (<~ 30 AU) and can be identified observationally.