Exoplanets, -moons, -comets

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

By Keith Cowing

Status Report

astro-ph.EP

March 2, 2026

Filed under astro-ph.EP, exoplanet, hot jupiter, M dwarf, radius valley, sub-Neptune, super-Earth, TESS, wate world

TESS Planet Occurrence Rates Reveal the Disappearance of the Radius Valley Around Mid-to-Late M Dwarfs — Distribution of our found planets in period–radius space (left) and instellation–radius space (right). Each planet and its associated errors are are marked with the red points, while the background grid shows the peak occurrence rate fpeak in each bin of the grid. Regions where our average sensitivity is < 10% are highlighted in pink. The top and leftmost panels show the cumulative fpeak distributions from each map. We note that these distributions are not representative of the full occurrence rates, and differ because planets may find themselves in different regions of sensitivity based on their instellation and period. -- astro-ph.EP

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.

Erik Gillis, Ryan Cloutier, Emily Pass

Comments: Submitted to AAS Journals February 26 2026, 25 pages, 17 Figures, 8 Tables
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2602.23364 [astro-ph.EP] (or arXiv:2602.23364v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2602.23364
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Submission history
From: Erik Gillis Mr
[v1] Thu, 26 Feb 2026 18:59:48 UTC (20,029 KB)
https://arxiv.org/abs/2602.23364

Astrobiology,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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