Post-disk Evolution of Short-period Gas Giants in Compact Multi-planet Systems: A Mechanism to Produce the Observed Companionship Dichotomy Between Hot Jupiters and Warm Jupiters

Despite decades of effort, the dominant formation and evolution mechanisms for short-period gas giants remain contested. Previous searches for nearby planetary companions to hot Jupiters (P<10 d) have indicated that they are often isolated, which suggests that these close-in giants may have dynamically violent formation and evolutionary histories. In contrast, their wider-orbiting giant counterparts, known as warm Jupiters, have been more commonly observed to host nearby companions, implying that their dynamical histories are relatively quiescent. In this study, we adopt a unified formation framework for both populations of giants, wherein they exist within compact multi-super-Earth systems upon the disappearance of the protoplanetary disk. Considering only single-giant systems, we use numerical simulations to show that post-disk dynamical evolution can explain the observed dichotomy in the nearby low-mass companion rate for hot and warm Jupiters. Compared to most wider-orbiting giants, the shortest-period hot Jupiters in our systems host long and highly chaotic chains of consecutive super-Earths, which leads their low-mass companions to often end up on faraway and mutually inclined orbits. In addition to offering a possible explanation for the observed companionship dichotomy between hot Jupiters and warm Jupiters, our framework presents other testable predictions for the companionship trends of short-period giants.