The long-term evolution of planetary system architectures

The evolution and stability of planetary system architectures, key to planetary habitability, remains poorly understood. Both interactions between neighboring planets as well as between the planets and their host star can sculpt planetary systems on long (> Gyr) timescales. Characterizing the planet population of post-main-sequence stars can reveal the relative strength and frequency of these interactions, playing a crucial role in helping us to understand the past, present and future of planetary systems. Here we present new planetary systems discovered so far by the TESS Giants Transiting Giants program. With star and planet mass and radius constraints, we constrain the rate and efficiency of star-planet and planet-planet interactions in these systems. We find that planets transiting evolved stars display unique atmospheric inflation trends, where evolved hot Jupiters appear less inflated than similar main sequence hot Jupiters, while evolved hot Neptunes appear more inflated than their main sequence counterparts. We also find that these systems generally follow a monotonic period-eccentricity relation, where longer-period planets have higher eccentricities. Future studies of these systems can probe spin-orbit alignment, planet atmospheric composition, and planet multiplicity, revealing how long different planetary architectures might survive.