Moderately Eccentric Warm Jupiters from Secular Interactions with Exterior Companions

Abstract

Recent studies have proposed that most warm Jupiters (WJs, giant planets with semi-major axes in the range of 0.1-1 AU) probably form in-situ, or arrive in their observed orbits through disk migration. However, both in-situ formation and disk migration, in their simplest flavors, predict WJs to be in low-eccentricity orbits, in contradiction with many observed WJs that are moderately eccentric (e=0.2-0.7). This paper examines the possibility that the WJ eccentricities are raised by secular interactions with exterior giant planet companions, following in-situ formation or migration on a circular orbit. Eccentricity growth may arise from an inclined companion (through Lidov-Kozai cycles), or from an eccentric, nearly coplanar companion (through apsidal precession resonances). We quantify the necessary conditions (in terms of the eccentricity, semi-major axis and inclination) for external perturbers of various masses to raise the WJ eccentricity. We also consider the sample of eccentric WJs with detected outer companions, and for each system, identify the range of mutual inclinations needed to generate the observed eccentricity. For most systems, we find that relatively high inclinations (at least $\sim 40^{\circ }$) are needed so that Lidov-Kozai cycles are induced; the observed outer companions are typically not sufficiently eccentric to generate the observed WJ eccentricity in a low-inclination configuration. The results of this paper place constraints on possibly unseen external companions to eccentric WJs. Observations that probe mutual inclinations of giant planet systems will help clarify the origin of eccentric WJs and the role of external companions.

16 pages, 10 figures, accepted for publication in MNRAS

References in corpus (11)

• Make Super-Earths, Not Jupiters: Accreting Nebular Gas onto Solid Cores at 0.1 AU and Beyond
• The Exoplanet Orbit Database II: Updates to exoplanets.org
• Hot Jupiters from Coplanar High-eccentricity Migration
• Steady-state planet migration by the Kozai-Lidov mechanism in stellar binaries
• Kepler-432: a red giant interacting with one of its two long period giant planets
• A Class of Warm Jupiters with Mutually Inclined, Apsidally Misaligned, Close Friends
• Kepler-432 b: a massive planet in a highly eccentric orbit transiting a red giant
• Eccentricity and Spin-Orbit Misalignment in Short-Period Stellar Binaries as a Signpost of Hidden Tertiary Companions
• Eccentric Companions to Kepler-448b and Kepler-693b: Clues to the Formation of Warm Jupiters
• Kepler-432 b: a massive warm Jupiter in a 52-day eccentric orbit transiting a giant star
• On the formation of hot and warm Jupiters via secular high-eccentricity migration in stellar triples

Cited by in corpus (2)

• Spin-Orbit Misalignment of Merging Black-Hole Binaries with Tertiary Companions
• Chaotic quadruple secular evolution and the production of misaligned exomoons and Warm Jupiters in stellar multiples