Hot Jupiters' Isolation Is Not Unique to High-Eccentricity Tidal Migration

Abstract

Conventionally, the observed isolation of hot Jupiters, marked by a paucity of nearby low-mass planetary companions, has been interpreted as evidence of high-eccentricity tidal migration for these close-in gas giants. This loneliness is in stark contrast with the compact configurations commonly observed for warm Jupiters, indicating a curious dichotomy in dynamical origins between these two classes of short-period giants. In this study, however, we adopt a unified quiescent framework for both giant populations wherein they emerge from the protoplanetary disk as the sole Jovian planet within a compact multi-super-Earth system. We use long-term numerical simulations to show that post-disk dynamical evolution will naturally result in an observed preferential isolation for hot Jupiters relative to warm Jupiters. Specifically, their companions achieve significantly larger period ratios and mutual inclinations, rendering them more difficult to detect - especially via the transit method. Additionally, we find that this paradigm is consistent with the enigmatic population of longer-period hot Jupiters hosting interior companions on coplanar orbits. Another prediction of this model, best tested through high-precision Doppler campaigns, is the existence of a population of close-in (P<50 days) but mutually inclined outer companions to hot Jupiters.