Hidden Gems in TESS: sherlock finds two new rocky planets around nearby M dwarfs
Pith reviewed 2026-05-21 14:49 UTC · model grok-4.3
The pith
Two new rocky planets were found orbiting nearby M dwarfs by searching TESS data below standard detection thresholds.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The Hidden Gems project searches the TESS data for additional planets transiting low-mass stars in confirmed systems using sherlock, a specialized pipeline for robust detection and vetting of transit signals. This search yielded two inner rocky planets: TOI-237 c with radius 1.21 Earth radii on a 1.74-day orbit near 3:1 resonance with the outer planet, and TOI-4336 A c with radius 1.17 Earth radii on a 7.58-day orbit around an M3.5 star in a hierarchical triple. Ground-based photometry confirms both signals, circular-orbit models are statistically preferred, and the systems remain stable under dynamical simulations with TTV amplitudes of only seconds for TOI-237.
What carries the argument
sherlock, a specialized pipeline for robust detection and vetting of transit signals in TESS data that operates below the thresholds set by the SPOC and QLP pipelines
If this is right
- Both planetary systems remain dynamically stable over long timescales.
- Expected transit timing variations in the TOI-237 system are only a few seconds in amplitude.
- TOI-237 c is a viable target for JWST/MIRI phase-curve observations because of the small host-star radius and short orbital period.
- The two planets enlarge the known sample of warm super-Earths that lie below the radius valley.
Where Pith is reading between the lines
- Repeating the sherlock search across the full set of TESS M-dwarf systems could yield additional small planets that standard pipelines overlooked.
- Precise mass measurements of these planets would test whether they are truly rocky and help calibrate the radius-valley boundary for M-dwarf hosts.
- Because M dwarfs dominate the stellar population, the occurrence rate of such short-period super-Earths around them constrains models of planet formation and migration.
Load-bearing premise
The periodic dimming signals recovered by sherlock are produced by planets rather than by stellar activity, instrumental noise, or false-positive configurations.
What would settle it
High-cadence photometry or radial-velocity time series that show the signals are aperiodic, have depths inconsistent with the reported radii, or require implausibly high masses would falsify the planetary interpretation.
read the original 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.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript reports the discovery of two new rocky planets, TOI-237 c (radius 1.21 ± 0.04 R⊕, period 1.74 days) and TOI-4336 A c (radius 1.17 ± 0.06 R⊕, period 7.58 days), identified via the sherlock pipeline applied to TESS photometry of M-dwarf systems. These candidates are confirmed using ground-based transit photometry from TRAPPIST, SPECULOOS, ExTrA, and LCO facilities. The paper includes model comparisons favoring circular orbits, dynamical stability simulations, and notes on potential JWST phase-curve observations for TOI-237 c.
Significance. If the planetary interpretations hold, the work adds two warm super-Earths to the sample below the radius valley around nearby M dwarfs, with TOI-237 c highlighted for atmospheric follow-up due to its short period and small host star. The sherlock-based search for sub-threshold signals and the multi-facility confirmation provide a useful template for similar TESS analyses. Dynamical stability checks and circular-model preference are positive elements that support the claims when the false-positive risk is adequately addressed.
major comments (2)
- [Abstract and confirmation sections] Abstract and confirmation sections: the planetary nature is asserted based on sherlock vetting plus multi-facility ground photometry, yet no quantitative false-positive probability (FPP) is provided. For M-dwarf TESS candidates, especially in the hierarchical triple TOI-4336 A, standard practice requires an FPP estimate (e.g., via vespa or TRICERATOPS) incorporating blend scenarios and activity; its absence leaves the central confirmation claim vulnerable to activity mimics or unresolved eclipsing binaries.
- [Radius and parameter sections] Radius and parameter sections: the reported radii (1.21 ± 0.04 R⊕ and 1.17 ± 0.06 R⊕) lack an explicit error budget breaking down contributions from stellar radius, limb-darkening coefficients, detrending choices, or data-exclusion criteria. This is load-bearing for the classification as rocky planets below the radius valley and for any future JWST planning.
minor comments (2)
- [Abstract] The abstract states that circular models are statistically favored but does not specify the comparison metric (BIC, AIC, or Bayesian evidence ratio) or the exact model parameters varied.
- [Introduction and system descriptions] Notation for the two planets (TOI-237 c and TOI-4336 A c) is clear, but the manuscript should explicitly state whether the outer planets (TOI-237 b and TOI-4336 A b) were previously known or also discovered in this work.
Simulated Author's Rebuttal
We thank the referee for their constructive comments, which have helped us improve the clarity and robustness of the manuscript. We address each major comment below and have made revisions where appropriate to strengthen the presentation of our results.
read point-by-point responses
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Referee: [Abstract and confirmation sections] Abstract and confirmation sections: the planetary nature is asserted based on sherlock vetting plus multi-facility ground photometry, yet no quantitative false-positive probability (FPP) is provided. For M-dwarf TESS candidates, especially in the hierarchical triple TOI-4336 A, standard practice requires an FPP estimate (e.g., via vespa or TRICERATOPS) incorporating blend scenarios and activity; its absence leaves the central confirmation claim vulnerable to activity mimics or unresolved eclipsing binaries.
Authors: We agree that an explicit quantitative FPP estimate would further bolster the confirmation claims, particularly given the hierarchical triple nature of TOI-4336 A. Our original analysis relied on sherlock vetting combined with multi-facility ground photometry to rule out false positives, but we acknowledge that this does not replace a formal FPP calculation. In the revised manuscript we have added FPP estimates computed with TRICERATOPS for both systems. These calculations incorporate blend scenarios, stellar activity, and the specific architecture of the TOI-4336 triple system, yielding low FPP values that support the planetary interpretation. revision: yes
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Referee: [Radius and parameter sections] Radius and parameter sections: the reported radii (1.21 ± 0.04 R⊕ and 1.17 ± 0.06 R⊕) lack an explicit error budget breaking down contributions from stellar radius, limb-darkening coefficients, detrending choices, or data-exclusion criteria. This is load-bearing for the classification as rocky planets below the radius valley and for any future JWST planning.
Authors: We appreciate the request for a more detailed error budget, as this improves transparency for readers interested in the rocky-planet classification and potential JWST observations. The quoted radius uncertainties already incorporate the dominant contributions from stellar radius and transit depth, but we agree that an itemized breakdown is valuable. We have revised the parameter sections to include an explicit error budget that quantifies the separate contributions from stellar radius, limb-darkening coefficients, detrending choices, and data-exclusion criteria. The revised text shows that stellar radius uncertainty remains the leading term, consistent with the reported values and the placement below the radius valley. revision: yes
Circularity Check
Observational discovery paper with independent follow-up photometry exhibits no circularity
full rationale
The paper reports empirical detection of transit signals in TESS data via the sherlock pipeline, followed by confirmation through separate ground-based photometry from TRAPPIST, SPECULOOS, ExTrA, and LCO facilities. Central results are measured radii, periods, and stability checks from dynamical simulations; none reduce by construction to fitted inputs or self-citations. Model comparison favoring circular orbits is a data-driven statistical outcome, not a definitional loop. The derivation chain relies on external observational benchmarks rather than internal self-reference, making the result self-contained.
Axiom & Free-Parameter Ledger
free parameters (2)
- planet radius
- orbital period
axioms (2)
- domain assumption Transit signals are produced by planets rather than stellar activity or instrumental artifacts once vetted by sherlock and ground photometry.
- standard math Standard Keplerian dynamics and N-body stability apply to the multi-planet systems.
discussion (0)
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