Dynamical Instabilities in Post-Disk Evolution: Hot Jupiters Left Isolated

The predominant formation channel of hot Jupiters remain a puzzle in exoplanet science. One potential way to distinguish the different mechanisms is to study the characteristics of close-in companions to hot Jupiters. In this study, our main focus is to investigate the post-disk evolution of planetary systems initially composed of one Jupiter and several super-Earths through numerical N-body simulations spanning a period of 107 years. By tracing the evolution of each planetary system, we find that only 5.6% of the systems remain stable. Dynamical instabilities are more prevalent in systems with less massive super-Earths and those containing hot Jupiters. Our findings uncover a positive correlation between the presence of close-in companions and the orbital periods of the giant planets. Specifically, we find that approximately 10.9% ± 1.9% of hot Jupiters and 36.4% ± 1.8% of warm Jupiters have close-in companions after 107 years. Moreover, extending the integration time to 108 years reveals that only 1.4%±1.0% of hot Jupiters and 20.3%±2.2% of warm Jupiters host close-in companions. We also investigate the effects of general relativistic, tidal dissipation, and initial spacing between Jupiters and their neighboring planets on the frequency of close-in companions for these short period Jupiters. Our simulations suggest that the general relativity effect plays a crucial role in contributing to the isolation of hot Jupiters. Furthermore, we observe that the more compact the planetary systems are initially, the less likely it is for Jupiter to host close-in companions.