2026/02/26 by Erik Gillis, Erik Diego Gillis, Ryan Cloutier +1 · 2 voices
Physics and Astronomy · #Stellar, planetary, and galactic studies #Astronomy and Astrophysical Research #Scientific Research and Discoveries
paper · pdf · doi:10.3847/1538-3881/ae5810
Abstract We present the deepest systematic search for planets around mid-to-late M dwarfs to date. We have surveyed 8134 mid-to-late M dwarfs observed by the Transiting Exoplanet Survey Satellite with a custom-built pipeline and recover 77 vetted transiting planet candidates. We characterize the sensitivity of our survey via injection–recovery and measure the occurrence rate of planets as a function of orbital period, instellation, and planet radius. We measure a cumulative occurrence rate of 1.10 ± 0.16 planets per star with radii >1 R ⊕ orbiting within 30 days. This value is consistent with the cumulative occurrence rate around early M dwarfs, making M dwarfs collectively the most prolific hosts of small close-in planets. Unlike the bimodal radius valley exhibited by close-in planet populations around FGK and early M dwarfs, we recover a unimodal planet radius distribution peaking at 1.25 ± 0.05 R ⊕ . We additionally find 0.954 ± 0.147 super-Earths and 0.148 ± 0.045 sub-Neptunes per star, with super-Earths outnumbering sub-Neptunes 5.5:1, firmly demonstrating that the radius valley disappears around the lowest-mass stars. The dearth of sub-Neptunes around mid-to-late M dwarfs is consistent with predictions from water-rich pebble accretion models that predict a fading radius valley with decreasing stellar mass. Our results support the emerging idea that the sub-Neptune population around M dwarfs is composed of water-rich worlds. We find no hot Jupiters in our survey and set an upper limit of 0.012 hot Jupiters per mid-to-late M dwarf within 10 days.