Characterizing sub-Neptunes around M dwarfs: recent progress and TTV opportunities
Speaker: Akihiko Fukui (U. Tokyo)
Abstract:
Sub-Neptunes are the most common class of exoplanets in close-in orbits, yet their compositions and formation pathways remain poorly understood. The Kepler space telescope revealed the radius distribution of sub-Neptunes through the transit method; however, most of these planets lack mass measurements due to the faintness and large masses of their host stars, limiting our ability to infer their internal compositions. Recently, the all-sky transit survey satellite TESS has increased the number of transiting sub-Neptunes orbiting nearby M dwarfs, i.e., stars that are both bright and low in mass, enabling more mass measurements via the radial velocity method. This method is, however, less sensitive to the masses of longer period planets, leaving the mass-radius distribution of warm and cool sub-Neptunes largely unexplored. In this talk, I will review recent progress in the observation of transiting sub-Neptunes and introduce our project to observe transit timing variations (TTVs) in multi-sub-Neptune systems using the multiband camera series MuSCAT. The TTV technique has a unique sensitivity to the masses of relatively long-period, low-mass sub-Neptunes around M dwarfs, which could offer important clues to the formation and evolution of sub-Neptunes.