Speaker
Description
AU Mic is a highly active M dwarf star with an edge-on debris disk and two known transiting sub-Neptunes, with a possible third planetary companion. The two transiting planets exhibit significant transit-timing variations (TTVs). We conducted ultra-high-precision photometric observations with the CHaracterizing ExOPlanet Satellite (CHEOPS) in 2022 and 2023. We combined our new measurements with results from previous years to determine the periods and amplitudes of the TTVs. Using dynamical modeling based on TTV measurements from 2018 to 2023, we reconstructed the perceived variations. AU Mic c exhibited very strong TTVs, with transits occurring approximately 80 minutes later in 2023 than in 2021. Through a dynamical analysis of the system, we found that the observed TTVs can be explained by a third planet with an orbital period of about 12.6 days and a mass of approximately 0.203 Earth masses. We explored the system's orbital geometry and found that AU Mic c is very likely on a misaligned, retrograde orbit.
