Chaotic dynamics of stellar spin in binaries and the production of misaligned hot Jupiters

Abstract

Many exoplanetary systems containing hot Jupiters are observed to have highly misaligned orbital axes relative to the stellar spin axes. Kozai-Lidov oscillations of orbital eccentricity and inclination induced by a binary companion, in conjunction with tidal dissipation, constitute a major channel for the production of hot Jupiters. We demonstrate that gravitational interaction between the planet and its oblate host star can lead to chaotic evolution of the stellar spin axis during Kozai cycles. As parameters such as the planet mass and stellar rotation period are varied, periodic islands can appear in an ocean of chaos, in a manner reminiscent of other dynamical systems. In the presence of tidal dissipation, the complex spin evolution can leave an imprint on the final spin-orbit misalignment angles.

Spin–Orbit Misalignment of Merging Black Hole Binaries with Tertiary Companions

“…These behaviors are qualitatively similar to the chaotic evolution of stellar spin driven by Newtonian spin-orbit coupling with a giant planet undergoing high-eccentricity migration (Storch et al 2014;Storch & Lai 2015;Anderson et al 2016;Storch et al 2017).…”

“…The related precession rate Ω L is of order t −1 LK at e ∼ 0 (Equation 17), but increases with e. Depending on the ratio of Ω dS and Ω L , we expect three possible spin behaviors: (i) For Ω L Ω dS ("nonadiabatic"), the spin axisŜ 1 cannot "keep up" with the rapidly changingL, and thus effectively precesses aroundĴ, keeping θ SJ ≡ cos ("trans-adiabatic"), the spin evolution can be chaotic due to overlapping resonances. Since both Ω dS and Ω L depend on e during the LK cycles, the precise transitions between these regimes can be fuzzy (Storch et al 2014;Storch & Lai 2015;Anderson et al 2016;Storch et al 2017).…”

Stellar Spin–Orbit Alignment for Kepler-9, a Multi-transiting Planetary System with Two Outer Planets Near 2:1 Resonance

“…These include chaotic star formation (Bate et al 2010;Thies et al 2011;Fielding et al 2015) and evolution (Rogers et al 2012), magnetic torques from host stars (Lai et al 2011), and gravitational torques from distant companions (Tremaine 1991;Batygin et al 2011;Storch et al 2014). In these scenarios, spin-orbit misalignments are expected to be observed not only among star-hot Jupiter pairs, but also among a broader class of planetary systems, notably those that have never experienced chaotic migration processes.…”

The formation efficiency of close-in planets via Lidov–Kozai migration: analytic calculations

“…The known migration mechanisms can be (i) "disc mediated" due to planet-disc interaction (e.g., Goldreich & Tremaine 1980;Lin, Bodenheimer & Richardson 1996), (ii) "planet mediated", including strong planet-planet scatterings and various forms of secular interactions among multiple planets (e.g. Rasio & Ford 1996;Chatterjee et al 2008;Jurić & Tremaine 2008;Nagasawa, Ida & Bessho 2008;Wu & Lithwick 2011;Beaugé & Nesvorný 2012;Petrovich 2015a), or (iii) "binary mediated", i.e., secular interactions with a distant stellar companion (Wu & Murray 2003;Wu, Murray & Ramsahai 2007;Fabrycky & Tremaine 2007;Naoz, Farr & Rasio 2012;Correia et al 2011;Storch, Anderson & Lai 2014;Petrovich 2015b;Anderson, Storch & Lai 2016). Excluding disc-driven migration, these mechanisms require the migrating planet to reach high eccentricities in order for E-mail:dmunoz@astro.cornell.edu tidal dissipation at pericenter to shrink the planet semi-major axis down to 0.1 AU.…”