Revealing Imprints of Tidal Evolution and Radius Inflation with TESS Transiting Brown Dwarfs

Brown dwarfs (BDs) are important transition objects between stars and planets, whose formation and evolution are not well understood and appear to share characteristics with both planets and stars. Transiting brown dwarfs offers a valuable opportunity to understand the BD population, due to their precisely measured mass, radius, and sometimes, age and metallicity. These rare short-period star-BD systems also provide critical insights into tidal effects, such as spin-orbit synchronization, which is common in stars but rare among planetary systems. Here, we present our discovery of 4 transiting BDs, using TESS light curves along with ground-based photometric and radial velocity data. We will show the abnormally fast rotation of the two evolved stars TOI-1608 and TOI-2521 caused by tidal synchronization with their BD companions’ orbits, as well as the aligned but eccentric orbit in the young system TOI-1830, which may reflect an ongoing tidal evolution. In addition, we present the dependence of radius inflation on mass and stellar irradiation from the transiting BD sample and compare it with planets. These special systems provide valuable observational constraints for the formation and evolution of BDs and their tidal interactions.