The Formation of Double Hot Jupiter Systems through von Zeipel-Lidov-Kozai Migration

TL;DR

This paper explores how the von Zeipel-Lidov-Kozai mechanism with tidal friction can lead to the formation of double hot Jupiter systems in binary stars, using N-body simulations to analyze mirrored migration of two planets.

Contribution

It introduces a novel scenario for double hot Jupiter formation via ZLK migration in binary systems and assesses its robustness through simulations and parameter variations.

Findings

Double hot Jupiters could be present in up to ~9% of certain binary systems.

Mirrored ZLK migration can produce double hot Jupiters under specific conditions.

Searches should focus on twin binaries with close pericenter approaches.

Abstract

The von Zeipel-Lidov-Kozai (ZLK) mechanism with tidal friction has been demonstrated as a promising avenue to generate hot Jupiters in stellar binary systems. Previous population studies of hot Jupiter formation have largely examined this mechanism in systems comprised of three bodies: two stars and one planet. However, because stars in a binary system form in similar environments with comparable metallicities, the formation of a single hot Jupiter in such a system may imply that the conditions are more likely met for the companion star, as well. We investigate the ZLK mechanism with tidal friction as a potential mechanism to produce double hot Jupiter systems in stellar binaries. Using N-body simulations, we characterize the evolution of two cold Jupiters, each orbiting one star in a binary system, undergoing mirrored ZLK migration. We then examine the robustness of this mechanism to asymmetries in stellar masses, planet masses, and planet orbital inclinations relative to the binary plane. We predict that, under the assumptions that (1) most hot Jupiters in binary star systems form through ZLK migration of primordially formed cold Jupiters and (2) if one star in a binary system forms a cold Jupiter, the second does as well, a comprehensive search could identify double hot Jupiters in up to ~9% of the close- to moderate- separation $a<2000$ AU) binary systems that already host a known hot Jupiter. We also argue that a blind search for ZLK-migrated double hot Jupiters should prioritize twin stellar binaries with pericenter approaches of a few hundred AU.