Probing Physics of Evolved Stars and their Short Period Planetary Companions with TESS

Despite the discovery of thousands of planets orbiting various stars thoughout our Galaxy, star-planet interaction remain poorly understood. In particular, late-stage star-planet interaction has remained particularly elusive, largely due to the difficulties in detecting planets around evolved stars. However, the Full Frame Image data from the TESS mission has provided 30-min cadence light curves of hundreds of thousands of evolved stars across the sky. Here I will introduce the newest planet discoveries around these evolved stars, including the shortest-period planet ever discovered around a red giant star. These particularly short period systems have been predicted to decay quickly, but the timescale of orbital decay is strongly dependent on the stellar structure in these subgiant and low-luminosity red giant stars, which has not yet been accurately modeled. We introduce new constraints on tidally driven period decay in these systems, tidal qualities of the evolved host stars studied here and provide updated boundaries between convective and radiative cores in subgiant and red giant stars. Finally, we consider additional constraints on star and planet structure and evolution that can be deduced from the larger population of planet candidates around evolved stars observed by TESS.