TESS Planet Occurrence Rates Reveal the Disappearance
of the Radius Valley Around Mid-to-Late M Dwarfs

Gillis, Cloutier, & Pass 2026

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 TESS 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 >1R⊕ 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 population around FGK and early M dwarfs, we recover a unimodal planet radius distribution peaking at 1.25±0.05R⊕. 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.

Aligned Stellar Obliquities for Two Hot Jupiter-hosting M Dwarfs
Revealed by MAROON-X: Implications for Hot Jupiter Formation

Weisserman, Gillis, Cloutier, et al. 2025

Hot Jupiters (HJs) are 2−3x less common around early M dwarfs than around AFGK stars, suggesting that HJs may form and/or migrate via distinct pathways around different types of stars. One source of insight into HJ formation mechanisms is to trace their dynamical histories through measurements of host stellar obliquities via the Rossiter-McLaughlin (RM) effect. Here we present measurements of the RM effect for the HJs TOI-3714 b and TOI-5293 A b using the Gemini-North/MAROON-X spectrograph. Our measurements represent just the second and third hot Jupiters around M dwarfs (HJMD) with a detection of the RM effect. We find that both systems are well-aligned with sky-projected obliquities of λ=21+14−11∘ and −12+19−14∘ and deprojected obliquities of ψ=26+11−10∘ and 24+11−10∘ for TOI-3714 and TOI-5293 A, respectively. Both stars are in wide binary systems. We refine the stellar parameters by decontaminating their unresolved Ks-band photometry and constrain the binary orbits using Gaia DR3 astrometry. We find that the minimum mutual inclination of the planet and binary companion in the TOI-5293 system is sufficiently large to drive Kozai-Lidov (KL) migration while the result for TOI-3714 is inconclusive. We present a population-level analysis of HJs around AFGK versus early M dwarfs and argue that KL migration is more efficient around the latter, which is expected to produce misaligned stellar obliquities in HJMD systems in the absence of efficient tidal damping. The emerging population of well-aligned HJMD hosts supports the expectation that M dwarfs, with their deep convective envelopes, do efficiently dampen misaligned obliquities.

Telscopes & Instruments

NIRPS

I am a core science team member of NIRPS, the Near-Infrared Planet Searcher . NIRPS is a high-resolution near-infrared spectrograph at the ESO 3.6m telescope in La Silla, Chile and is optimized to detect and characterize small planets orbiting M dwarfs stars using the radial velocity method. NIRPS serves as the "red arm" of the optical spectrograph HARPS, which when operated simultaneously, provides extremely precise chromatic radial velocity measurements that enable astonomers to disentangle tiny planetary signals from stellar activity.
(Credit: N. Blind/Geneva Observatory/NIRPS/ESO Consortium)

SPIRou

SPectropolarimètre InfraROUge (SPIRou) is a near-infrared spectropolarimeter located at the Canada-France-Hawaii Telescope (CFHT) on Maunakea in Hawaii. SPIRou is optimized for high-precision radial velocity measurements of M dwarfs and is commonly used to find/characterize exoplanets and study stellar magnetic fields. We also use SPIRou in our group to measure the detailed elemental abundances of M dwarfs to inform our understanding of the interior compositions of the super-Earths and sub-Neptunes that orbit them.
(Credit: É Artigau)

TESS

NASA's Transiting Exoplanet Survey Satellite (TESS) mission is a multi-year, all-sky survey searching for the closest exoplanets to the solar system using the transit method. TESS's regular public data releases are a fixture of much of the research being done in our group. I am also a member of the TESS Follow-up Observing Program (TFOP), which conducts a variety of follow-up observations to confirm TESS planet candidates, including the precise measurement of planet masses using the radial velocity method.
(Credit: NASA/JPL-Caltech)

Ariel (planned 2029)

I am a member of CAST, the Canadian Ariel Science Team, in support of the European Space Agency's Ariel mission (Atmospheric Remote-sensing Infrared Exoplanet Large-survey). Ariel will study the atmospheres of about a thousand planets around other stars, including rocky planets and gas giants, to discover the chemical ingredients that make up their atmospheres. The mission will also study planets' clouds and atmospheric dynamics by monitoring variations over time.
(Credit: ESA/Ariel)

CASTOR (planned 2030s)

The Cosmological Advanced Survey Telescope for Optical and uv Research (CASTOR) is a proposed Canadian flagship mission with the Canadian Space Agency. CASTOR's unique photometric and spectroscopic capabilities in the ultraviolet to the blue-optical will address a wide range of topics from the solar system to cosmology. I am a CASTOR science team member focusing on the Stellar Astrophysics and Exoplanets working groups.
(Credit: NRC/CASTOR)