Possible Outcomes of Coplanar High-eccentricity Migration: Hot Jupiters, Close-in Super-Earths, and Counter-orbiting Planets

Abstract

We investigate the formation of close-in planets in near-coplanar eccentric hierarchical triple systems via the secular interaction between an inner planet and an outer perturber (Coplanar High-eccentricity Migration; CHEM). We generalize the previous work on the analytical condition for successful CHEM for point masses interacting only through gravity by taking into account the finite mass effect of the inner planet. We find that efficient CHEM requires that the systems should have m 1 ≪ m 0 and m 1 ≪ m 2 . In addition to the gravity for point masses, we examine the importance of the short-range forces, and provide an analytical estimate of the migration time scale. We perform a series of numerical simulations in CHEM for systems consisting of a sun-like central star, giant gas inner planet and planetary outer perturber, including the short-range forces and stellar and planetary dissipative tides. We find that most of such systems end up with a tidal disruption; a small fraction of the systems produce prograde hot Jupiters (HJs), but no retrograde one. In addition, we extend CHEM to super-Earth mass range, and show that the formation of close-in super-Earths in prograde orbits is also possible. Finally, we carry out CHEM simulation for the observed hierarchical triple and counter-orbiting HJ systems. We find that CHEM can explain a part of the former systems, but it is generally very difficult to reproduce counter-orbiting HJ systems.

Eccentric Companions to Kepler-448b and Kepler-693b: Clues to the Formation of Warm Jupiters

“…I compute secular evolution of both the inner and outer orbits along with the spins of the star and inner planet. I use the code developed and utilized in Xue & Suto (2016) and Xue et al (2017), which takes into account (i) gravitational interaction up to the octupole order and (ii) precessions due to general relativity as well as tidal and rotational deformation of the bodies. Here I neglect magnetic braking of the star and tidal dissipation inside the bodies, and assume zero stellar and planetary obliquities for simplicity.…”

Dynamical Evolution of Closely Packed Multiple Planetary Systems Subject to Atmospheric Mass Loss

“…In situ formation of these super-Earths requires disk surface density in planetesimals to be many orders of magnitude larger than that extrapolated from the minimum mass nebula scenario (Ida & Lin 2004;Wang et al 2012;Chiang & Laughlin 2013;Tamayo et al 2017). Although high-eccentricity migration due to planet-planet scattering (Rasio & Ford 1996;Lin & Ida 1997;Beauge & Nesvorny 2012), Kozai resonance (Wu & Murray 2003;Anderson et al 2016), and secular chaos (Nagasawa et al 2008;Wu & Lithwick 2011;Hamers et al 2017) can lead to the relocation of close-in Jupiter-mass gas giants, the configurations of MMRs in multiple super-Earth systems are difficult to accomplish (Giacalone et al 2017;Xue et al 2017) in these circumstances.…”

Disentangling the stellar inclination of transiting planetary systems: fully analytic approach to the Rossiter-McLaughlin effect incorporating the stellar differential rotation

“…Such a naive expectation, however, is not necessarily the case for the observed distribution of λ (Xue et al 2014;Winn & Fabrycky 2015); more than 20 percents of transiting close-in gas-giant planets are misaligned, in the sense that the 2σ lower limit of their measured λ exceeds 30 • (Kamiaka et al 2019). While the origin of such a misalignment is not yet well understood, possible scenarios include planetary migration (Lin et al 1996), planet-planet scattering (Rasio & Ford 1996;Nagasawa et al 2008;Nagasawa & Ida 2011), and perturbation due to distant outer objects (e.g., Kozai 1962;Lidov 1962;Fabrycky & Tremaine 2007;Batygin 2012;Xue et al 2014Xue et al , 2017.…”