Hidden Gems in TESS: sherlock finds two new rocky planets around nearby M dwarfs

Abstract

The Hidden Gems project searches the TESS data for additional planets transiting low-mass stars in confirmed systems. Our goal is to identify planet candidates that are below the detection threshold set by the SPOC and QLP pipelines using sherlock, a specialized pipeline for robust detection and vetting of transit signals in TESS data. We present the discovery of two inner rocky planets in the TOI-237 and TOI-4336 A systems, confirmed with ground-based photometry from the TRAPPIST, SPECULOOS, ExTrA, and LCO facilities. TOI-237 c has a radius of 1.21 +/- 0.04Re, orbits its mid-M host star every 1.74 days, and is close to a 3:1 mean-motion resonance with TOI-237 b. TOI-4336 A c has a radius of 1.17 +/- 0.06Re, and orbits with a period of 7.58 days an M3.5 host star which is part of a hierarchical triple system. We performed model comparison to search for non-zero eccentricities, and found that the circular transit models are statistically favored. Dynamical simulations show that both systems are in stable configurations, and the TTVs expected for the TOI-237 system are of the order of seconds. TOI-237 c and TOI-4336 A c join the high-interest population of warm likely super-Earths below the so-called "radius valley". In particular, TOI-237 c is a good candidate for phase curve observations with JWST/MIRI thanks to the small radius of the host star and its short period.

20 pages, 13 figures, submitted to MNRAS, in review. Comments will be implemented in an updated version on ArXiv. This is a coordinated pre-print submission with Parc et al. 2026

References in corpus (36)

• Gaia Data Release 3: Summary of the content and survey properties
• The Transiting Exoplanet Survey Satellite
• The K2 Mission: Characterization and Early results
• How to Constrain Your M Dwarf: measuring effective temperature, bolometric luminosity, mass, and radius
• Constraining the Age-Activity Relation for Cool Stars: The SDSS DR5 Low-Mass Star Spectroscopic Sample
• The TESS Objects of Interest Catalog from the TESS Prime Mission
• A stellar-mass-dependent drop in planet occurrence rates
• Density, not radius, separates rocky and water-rich small planets orbiting M dwarf stars
• Transit Least Squares: Optimized transit detection algorithm to search for periodic transits of small planets
• Revised metallicity classes for low-mass stars: dwarfs (dM), subdwarfs (sdM), extreme subdwarfs (esdM), and ultra subdwarfs (usdM)
• Gaia Data Release 3: Processing and validation of BP/RP low-resolution spectral data
• Gaia Data Release 3: External calibration of BP/RP low-resolution spectroscopic data
• Vetting of 384 TESS Objects of Interest with TRICERATOPS and Statistical Validation of 12 Planet Candidates
• ARIADNE: Measuring accurate and precise stellar parameters through SED fitting
• Kepler-445, Kepler-446 and the Occurrence of Compact Multiples Orbiting Mid-M Dwarf Stars
• Internal calibration of Gaia BP/RP low-resolution spectra
• Occurrence Rates of Planets Orbiting M Stars: Applying ABC to Kepler DR25, Gaia DR2, and 2MASS Data
• SPECULOOS -- Ultracool Dwarf Transit Survey: Target List and Strategy
• A super-Earth and a sub-Neptune orbiting the bright, quiet M3 dwarf TOI-1266
• Architectures of Exoplanetary Systems. III: Eccentricity and Mutual Inclination Distributions of AMD-stable Planetary Systems
• Masses and compositions of three small planets orbiting the nearby M dwarf L231-32 (TOI-270) and the M dwarf radius valley
• Two temperate super-Earths transiting a nearby late-type M dwarf
• Optical Spectroscopic Classification and Membership of Young M Dwarfs in Star-Forming Regions
• From super-Earths to sub-Neptunes: Observational constraints and connections to theoretical models
• prose: A Python framework for modular astronomical images processing
• GJ 273: On the formation, dynamical evolution and habitability of a planetary system hosted by an M dwarf at 3.75 parsec
• A super-Earth and a mini-Neptune near the 2:1 MMR straddling the radius valley around the nearby mid-M dwarf TOI-2096
• A 1.55 R${}_{\oplus }$ habitable-zone planet hosted by TOI-715, an M4 star near the ecliptic South Pole
• GJ357: A low-mass planetary system uncovered by precision radial-velocities and dynamical simulations
• The SHERLOCK pipeline: new exoplanet candidates in the WASP-16, HAT-P-27, HAT-P-26, and TOI-2411 systems
• TOI 122b and TOI 237b, two small warm planets orbiting inactive M dwarfs, found by \textit{TESS}
• Two warm Earth-sized exoplanets and an Earth-sized candidate in the M5V-M6V binary system TOI-2267
• TOI-4336 A b: A temperate sub-Neptune ripe for atmospheric characterization in a nearby triple M-dwarf system
• Infrared photometry with InGaAs detectors: First light with SPECULOOS
• Radius valley scaling among low mass stars with TESS
• Densities of small planets around the M dwarfs TOI-4336 A and TOI-4342 with ESPRESSO: Three sub-Neptunes, one super-Earth, and a Neptune-mass candidate