Recognition: 1 theorem link
· Lean TheoremConfirmation of the hot super-Neptune TOI-672 b with NIRPS and HARPS and Insights into the Neptunian desert around M dwarfs
Pith reviewed 2026-05-15 11:31 UTC · model grok-4.3
The pith
Confirmation of super-Neptune TOI-672 b shows the Neptunian desert boundary is statistically similar for M dwarfs and FGK stars.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The central claim is that TOI-672 b is a confirmed single-planet system with measured period 3.634 days, radius 5.31 Rearth, and mass 50.9 Mearth. A novel boundary-determination technique applied to the observed planet population shows the Neptunian ridge at 3.3 plus or minus 1.4 days for FGK hosts and 2.2 plus or minus 1.0 days for M-dwarf hosts; these values do not differ at a statistically significant level, and the inward shift for M dwarfs is smaller than photoevaporation models predict.
What carries the argument
A novel statistical method for locating the Neptunian desert boundaries in period-radius and instellation-radius space, applied separately to FGK and M-dwarf subsamples to test for differences.
If this is right
- TOI-672 b is the only detectable planet in its system within current RV and TTV sensitivity limits.
- The Neptunian ridge position shifts only modestly inward around M dwarfs compared with FGK stars.
- Photoevaporation models that predict a larger stellar-type dependence are inconsistent with the observed boundary locations.
- The measured mass and radius of TOI-672 b constrain its bulk composition and envelope retention at the desert edge.
Where Pith is reading between the lines
- The similarity of boundaries suggests high-eccentricity migration followed by circularization operates at comparable efficiency around M dwarfs.
- Additional short-period Neptunes around early M dwarfs could be searched for with NIRPS to test whether the ridge population is as dense as around FGK stars.
- The planet's high mass at this radius may indicate that core-accretion efficiency differs around lower-mass stars.
Load-bearing premise
The novel approach to determining the Neptunian desert boundaries accurately reflects the true underlying distribution without significant selection biases or incomplete sampling in the planet catalogs used.
What would settle it
Detection of a statistically significant difference in ridge location when the M-dwarf planet sample is enlarged by a factor of two would falsify the claim that the boundaries do not differ between stellar types.
read the original abstract
The Neptunian desert is a distinct lack of Neptune-sized planets at short orbital periods, purportedly carved by photoevaporation and tidal circularization following high-eccentricity migration. Constraining these processes and how they vary across different host-star spectral types requires the detailed characterization of planets in the desert and around its boundaries. In this study, we confirm the planetary nature of a massive super-Neptune identified by TESS around the M0 dwarf TOI-672. We analyse photometry from TESS and ExTrA and precise radial velocity measurements taken with the recently commissioned Near-InfraRed Planet Searcher (NIRPS) and HARPS spectrographs. We measure the planetary orbital period, radius, and mass of 3.634 days, 5.31 +0.24 -0.26 Rearth, and 50.9 +4.5 -4.4 Mearth, respectively. Our findings place TOI-672 b within the Neptunian ridge, a pile-up of planets from 3--5 days at the Neptunian desert boundary. We then use a novel approach to determine the desert boundaries in period-radius space and instellation-radius space, and, for the first time, compare the Neptunian desert boundaries for planets orbiting FGK versus M dwarf stars. We determine that the boundary ridge shifts slightly inward from 3.3 +- 1.4 days for FGK host stars to 2.2 +- 1.0 days for M dwarf host stars; these values do not statistically significantly differ from each other, and the shift to shorter periods for M dwarf planets is smaller than theoretical photoevaporation models predict. We also find that TOI-672 b is a single-planet system within the sensitivity limits of our RV and TTV datasets.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper confirms the planetary nature of TOI-672 b, a hot super-Neptune orbiting an M0 dwarf, using TESS and ExTrA photometry combined with radial velocities from the new NIRPS instrument and HARPS. It reports an orbital period of 3.634 days, radius of 5.31^{+0.24}_{-0.26} R_earth, and mass of 50.9^{+4.5}_{-4.4} M_earth, locating the planet in the Neptunian ridge at the desert boundary. The work introduces a novel statistical approach to map the desert boundaries in period-radius and instellation-radius space and performs the first comparison between FGK and M-dwarf host populations, finding a modest inward shift of the period ridge from 3.3 ± 1.4 days (FGK) to 2.2 ± 1.0 days (M dwarfs) that is not statistically significant and smaller than photoevaporation model predictions. The system is reported as single-planet within the sensitivity of the RV and TTV data.
Significance. If the novel boundary method can be shown to properly account for survey completeness, this manuscript would provide a valuable empirical anchor for how the Neptunian desert and its ridge vary with stellar mass, directly testing the relative roles of photoevaporation and tidal migration around M dwarfs. The precise mass and radius for TOI-672 b also strengthen the sample of well-characterized planets at the desert edge.
major comments (2)
- [Boundary determination section] Boundary determination section: The novel procedure used to locate the period ridge and desert edges is described only at a summary level. No explicit validation is provided that the method incorporates M-dwarf-specific completeness corrections (e.g., lower transit probability due to smaller stellar radii, reduced RV semi-amplitude sensitivity, or survey selection functions). Because the headline claim that the ridge shift (3.3 ± 1.4 d to 2.2 ± 1.0 d) is not statistically significant and is smaller than photoevaporation models rests on these boundary locations, the absence of injection-recovery tests stratified by spectral type or catalog bias modeling is a load-bearing gap.
- [Comparison to theoretical models paragraph] Comparison to theoretical models paragraph: The statement that the observed M-dwarf shift is smaller than predicted is presented without quoting the specific photoevaporation model parameters, grid resolution, or quantitative metric used for the comparison. This prevents the reader from assessing whether the discrepancy is robust or sensitive to model assumptions.
minor comments (3)
- [Figure captions] Figure captions for the boundary plots should explicitly state whether the plotted points include only confirmed planets or also candidates, and whether error bars on period and radius are shown.
- [Abstract and §3] The uncertainty notation in the abstract and main text is inconsistent (e.g., +0.24 -0.26 versus ±). Adopt a uniform format such as 5.31^{+0.24}_{-0.26} R_⊕ throughout.
- [Planet placement paragraph] The claim that TOI-672 b lies 'within the Neptunian ridge' would be clearer if the ridge definition (e.g., the exact period range or density threshold) were restated when the planet is first discussed.
Simulated Author's Rebuttal
We thank the referee for their constructive comments and positive assessment of the manuscript's significance. We address both major comments below by expanding the relevant sections with additional methodological details, validation tests, and model specifications. These revisions will strengthen the robustness of our boundary determination and model comparison claims.
read point-by-point responses
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Referee: [Boundary determination section] Boundary determination section: The novel procedure used to locate the period ridge and desert edges is described only at a summary level. No explicit validation is provided that the method incorporates M-dwarf-specific completeness corrections (e.g., lower transit probability due to smaller stellar radii, reduced RV semi-amplitude sensitivity, or survey selection functions). Because the headline claim that the ridge shift (3.3 ± 1.4 d to 2.2 ± 1.0 d) is not statistically significant and is smaller than photoevaporation models rests on these boundary locations, the absence of injection-recovery tests stratified by spectral type or catalog bias modeling is a load-bearing gap.
Authors: We agree that the boundary determination method requires more explicit validation to support the headline claims. In the revised manuscript, we will expand this section with a step-by-step description of the novel statistical procedure, including how M-dwarf-specific completeness corrections are incorporated (accounting for transit probability, RV semi-amplitude sensitivity, and survey selection functions). We will also add results from injection-recovery tests stratified by spectral type and catalog bias modeling to validate the boundary locations in period-radius and instellation-radius space. This will directly address the load-bearing gap and allow readers to assess the reliability of the reported ridge shift from 3.3 ± 1.4 days (FGK) to 2.2 ± 1.0 days (M dwarfs). revision: yes
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Referee: [Comparison to theoretical models paragraph] Comparison to theoretical models paragraph: The statement that the observed M-dwarf shift is smaller than predicted is presented without quoting the specific photoevaporation model parameters, grid resolution, or quantitative metric used for the comparison. This prevents the reader from assessing whether the discrepancy is robust or sensitive to model assumptions.
Authors: We acknowledge that the model comparison lacks the necessary specificity. In the revised manuscript, we will expand the relevant paragraph to quote the exact photoevaporation model parameters (e.g., mass-loss rates, XUV flux prescriptions, and core mass assumptions from the grids employed), the grid resolution used, and the quantitative metric for comparison (e.g., the difference in boundary periods with associated uncertainties). This will enable readers to evaluate the robustness of our conclusion that the observed M-dwarf shift is smaller than predicted and assess sensitivity to model assumptions. revision: yes
Circularity Check
No circularity: parameters and boundaries derived from independent data and catalogs
full rationale
The planetary period, radius, and mass are obtained from TESS/ExTrA photometry and NIRPS/HARPS radial velocities, which are external datasets. The novel boundary-determination procedure is applied to existing planet catalogs to compare FGK and M-dwarf samples; the resulting ridge locations (3.3 ± 1.4 d vs. 2.2 ± 1.0 d) and non-significance statement follow directly from that catalog analysis without any quoted reduction to a self-fit, self-citation chain, or redefinition of the target planet itself. No load-bearing step collapses by construction to the paper's own inputs.
Axiom & Free-Parameter Ledger
free parameters (2)
- FGK boundary period =
3.3 days
- M-dwarf boundary period =
2.2 days
axioms (1)
- domain assumption The observed planet sample around FGK and M dwarfs is representative and complete enough to define true desert boundaries
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discussion (0)
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