REVIEW 4 major objections 6 minor 4 references
Three Warm Jupiters orbiting TOI-6628, TOI-3837, TOI-5027 and one sub-Saturn orbiting TOI-2328
T0 review · 4 major / 6 minor · reviewed 2026-08-11 · deepseek-v4-flash
Pith's one-line read This paper confirms four transiting giant planets and reports that TOI-6628 b has one of the most eccentric orbits known among warm Jupiters.
desk verdict Four well-characterized warm giants, including a high-eccentricity outlier whose headline eccentricity is robust against a circular orbit but untested against a distant companion. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The argument is carried by a joint Bayesian fit (the juliet package) of TESS and ground-based transit light curves together with radial-velocity time series, using an eccentric Keplerian orbit, quadratic limb darkening, and per-instrument offsets and jitter; periodicity is first found with BLS and GLS periodograms. Planet radii and masses come from the combined photometric depth and RV semi-amplitude, and compositions are derived by comparing measured masses, radii, and ages to the GASTLI and MESA interior models, both assuming a rocky-icy core and H/He envelope.
What would settle it
Take high-resolution imaging of TOI-6628, TOI-5027, and TOI-2328 at sub-arcsecond resolution and a contrast of a few magnitudes; detection of a blended companion within the TESS aperture would change the required dilution, and re-fitting the transits with free dilution would shift the quoted radii. For TOI-3837 b, additional radial velocities that push the eccentric-orbit model's log-evidence above 5 relative to a circular orbit would confirm its measured eccentricity.
Extended reading notes
Core claim
The authors establish that TOI-6628 b, TOI-3837 b, TOI-5027 b, and TOI-2328 b are genuine transiting planets rather than false positives from blended binaries or stellar activity. Combining TESS photometry with ground-based transit light curves and radial velocities from FEROS, HARPS, and PFS, they derive self-consistent orbital solutions: TOI-6628 b has mass 0.75±0.06 MJ, radius 0.98±0.05 RJ, period 18.18424 days, and eccentricity 0.667±0.016; TOI-3837 b has mass 0.59±0.06 MJ, period 11.88865 days, eccentricity 0.198; TOI-5027 b is the most massive at 2.01±0.13 MJ with period 10.24368 days and eccentricity 0.395; TOI-2328 b is a sub-Saturn at 0.16±0.02 MJ with period 17.10197 days and near-circular orbit. For TOI-3837 b, a dedicated blend analysis rejects a stellar eclipsing binary explanation. Interior structure models then yield bulk metal mass fractions, with the four planets showing a rocky-icy core plus H/He envelope and metal enrichment consistent with core accretion.
Load-bearing premise
The transit signals are assumed to come from the target stars alone: photometric dilution is fixed to unity for every dataset except the explicit blend modeling of TOI-3837 b, so an unresolved companion or blended eclipsing binary on the other three targets would change the inferred radii, masses, and eccentricities.
Editorial extensions
If this is right
- TOI-6628 b adds a 0.67-eccentricity warm giant to a population where only about 5% of known giants have e>0.5, sharpening tests of high-eccentricity migration.
- The three eccentric systems (TOI-6628 b, TOI-3837 b, TOI-5027 b) occupy a sparse region of the period–eccentricity plane, providing evidence that warm giants retain a wider eccentricity distribution than hot Jupiters.
- Interior retrievals put the four planets on the mass–bulk metallicity trend defined by other warm giants, with TOI-5027 b slightly metal-rich, a composition pattern expected if core accretion proceeds with pebble and vapour-enriched gas.
- Predicted Rossiter–McLaughlin amplitudes of 23–54 m/s make these systems promising targets for measuring spin–orbit obliquity, which can discriminate migration channels.
Reading between the lines
- If TOI-6628 b's high eccentricity is robust, the most likely formation path involves planet–planet scattering or secular perturbations that first excited the orbit, with the current 18-day period requiring that tidal circularization has not yet completed; a search for outer companions in the reported linear RV trends would test this.
- High-resolution imaging of TOI-6628 and TOI-2328 at sub-arcsecond scales could reveal companions that would dilute the transit depth; without it, the fractional radius and derived density carry an unquantified systematic risk.
- The reported eccentricity of TOI-3837 b rests on a log-evidence difference below 5 relative to a circular orbit, so the eccentricity should be treated as tentative until more radial velocities arrive.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. This manuscript reports the discovery and characterization of four transiting giant planets: TOI-6628 b, TOI-3837 b, TOI-5027 b, and TOI-2328 b. The analysis combines TESS light curves with ground-based photometry from multiple small telescopes and radial velocities from FEROS, HARPS, and PFS, and fits the data with the juliet package under four nested models (no planet, circular single planet, eccentric single planet, eccentric single planet plus linear trend). The paper reports masses, radii, periods, eccentricities, and stellar parameters for all four systems, and interprets the mass-radius constraints with GASTLI and MESA interior models. The headline result is TOI-6628 b: a 0.75 MJ, 0.98 RJ planet on an 18.18 day orbit with eccentricity 0.667 ± 0.016, claimed to be one of the most eccentric warm giants known.
Significance. If the results hold, the paper adds four well-characterized transiting planets in the relatively sparse warm-Jupiter and sub-Saturn regime (P > 10 days), with particular value in the high-eccentricity orbit of TOI-6628 b and the bulk metal fractions derived for all four planets. The work makes good use of independent photometric and spectroscopic datasets: the multi-transit TESS detections are supported by ground-based photometry, the RV signals are coherent with the transit ephemerides, and Bayesian model comparisons are used to discriminate orbital models. The authors are also appropriately transparent about limitations: they state that the eccentricity of TOI-3837 b is not strongly preferred over a circular orbit, they note linear trends in RV residuals for three systems, and they flag the Teq = 1000 K approximation used for the two hottest planets in the interior modeling. These explicit caveats are a strength of the paper. The main risks lie in the fixed dilution factors for two targets without high-resolution imaging and in the single-Keplerian interpretation of the TOI-6628 b eccentricity.
major comments (4)
- [Section 2.1; Tables 6-9] The dilution factor md is fixed to 1.0 for every photometric dataset in Tables 6-9, but high-resolution imaging is presented only for TOI-3837 and TOI-5027 (Section 2.6). For TOI-6628, a 14.13 mag star lies near the TESS aperture (Section 2.1), and for TOI-2328 no high-resolution imaging is reported. An unresolved or partially resolved companion could dilute the transit signal and bias the inferred radii and densities, which are central to the reported bulk properties. The authors should either obtain or analyze high-angular-resolution imaging for TOI-6628 and TOI-2328, or quantitatively bound the dilution using the available Gaia and ground-based photometry and propagate that uncertainty into Rp and ρp.
- [Section 4.1.1; Table 4] The headline eccentricity e = 0.667 ± 0.016 for TOI-6628 b is derived from a single-planet eccentric Keplerian model. The paper states in Section 6 that linear trends in the RV residuals of TOI-6628 b suggest possible outer companions, and Table 4 shows that only a linear-trend model was tested, not a two-Keplerian model. Because an outer companion can be partially absorbed into a biased eccentricity and semi-amplitude for the inner planet, the authors should fit a two-Keplerian model (or provide a residual-periodogram and injection-recovery check) to demonstrate that e and K are not significantly shifted. The current evidence against the circular model is strong, but the robustness of the single-planet eccentric parameters to an additional companion is not established.
- [Section 5; Section 7] The statement that the interior models provide 'supporting evidence to the core accretion theory of planet formation' is stronger than the analysis supports. The GASTLI and MESA models assume a two-layer structure with a rock/water core and a H/He envelope, and the free CMF and envelope metallicity are fitted to the observed mass and radius; no alternative interior structures (e.g., metal-rich envelope without a distinct core, or a fully mixed interior) are tested. The Teq = 1000 K approximation for TOI-3837 b and TOI-5027 b is acknowledged, but the quoted ΔCMF = 0.02 for TOI-3837 b is a point estimate and is not propagated into the Table 5 uncertainties. I recommend softening the core-accretion conclusion or adding a comparison against alternative interior models.
- [Section 4.1; Table 4] For TOI-3837 b the Δlog-evidence between the eccentric and circular models is less than 5, and the paper correctly reports this. However, the discussion in Section 6 and the Conclusions list TOI-3837 b alongside the securely eccentric planets without restating this caveat. The text should carry the circular-orbit possibility through to the abstract and conclusions, or at least to the discussion, so that readers do not over-interpret e = 0.198 for this planet.
minor comments (6)
- [Abstract; throughout] There are multiple typos and grammatical slips: 'consistsent' appears in the abstract and elsewhere, 'consistss' appears in Section 2.2.2, and several sentences use singular/plural agreement incorrectly (e.g., 'Table 2.1 show'). A careful proofreading pass is needed.
- [Figure 12 caption] The left panel caption refers to 'TOI-6028 b'; this should be 'TOI-6628 b'.
- [Section 5] The reference 'see Table 2.2.2' for the planet mass prior should be Table 3; the current reference is nonsensical.
- [Tables A.1-A.4] Several activity-index entries appear implausibly large, for example HeI values of -18.728, -24.954, and -10.363 in Table A.1. The authors should check for unit errors or flag these as upper limits/excluded values.
- [Section 4; Figure 3] The sentence 'We observe a peak at the period of the RVs GLS peak' is confusing; it should be clarified that TOI-6628 shows an RV peak at the photometric period but below the 1% FAP threshold.
- [Section 2.2.2] The phrase 'the top second panel from left to right' is awkward; it should say 'the second panel from the left in the top row' or similar.
Circularity Check
Planet detections and bulk properties rest on independent TESS/RV/ground-based data, but the abstract's 'evidence supporting the core accretion model' reduces to the two-layer core+envelope ansatz built into GASTLI/MESA.
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self definitional
[Section 5 (Interior modelling) and Abstract / Section 6 discussion]
"The grid is stratified in two layers: a core composed of a 1:1 rock and water mixture, and an envelope constituted by H/He and water. ... our planet interior structure models are consistsent a rocky-icy core with a H/He envelope, providing evidence supporting the core accretion model of planet formation for this kind of planets."
The two-layer core-plus-envelope structure is a fixed assumption of the GASTLI model, not a free parameter tested against alternatives; the retrieval varies only CMF, envelope metallicity, and T_int to match observed mass and radius. The posterior is therefore guaranteed to be describable as a rocky core plus H/He envelope, and the statements that the planets 'consist of an icy and rocky core and a gaseous envelope' and that this 'provides evidence supporting the core accretion model' restate that input as an output. The MESA comparison uses the same assumption ('all of the heavy elements in the core, and a pure H/He gaseous envelope'), so agreement between the two codes does not add independent discrimination.
full rationale
The central detection claims are not circular: the transits are independently detected in TESS photometry, confirmed by ground-based light curves, and the RV signals are measured with three spectrographs; the orbital parameters, masses, and radii are fitted jointly to these independent data with explicit Bayesian model comparison (Table 4). The high eccentricity of TOI-6628 b is a direct fit parameter in the favored eccentric-Keplerian model and is not a renamed input; the acknowledged residual trend is a statistical caveat, not a circular reduction. There is no load-bearing self-citation chain: WINE collaboration papers and GASTLI are cited as tools/context, and the planet properties do not depend on an unverified self-cited uniqueness theorem. The one genuinely circular element is the interior-structure interpretation. Because GASTLI and the MESA setup assume a rocky/water core plus H/He envelope, the statement that the models are 'consistent with' that structure is tautological, and the further claim that this supports core accretion assumes the formation channel the interpretation claims to test. This affects the abstract's interpretive sentence and Section 6, but not the independent discovery/characterization results, so the overall circularity is partial rather than pervasive.
Assumptions & free parameters
free parameters (5)
- Core mass fraction (CMF) per planet =
TOI-6628 b: 0.11 +0.11/-0.08; TOI-3837 b: 0.08 +0.08/-0.05; TOI-5027 b: 0.47 +0.19/-0.24; TOI-2328 b: 0.29 +0.20/-0.16…
- Envelope metallicity log(Fe/H)_p per planet =
TOI-6628 b: -0.55 +1.04/-1.00; TOI-3837 b: -0.77 +0.95/-0.84; TOI-5027 b: -0.20 +1.59/-1.29; TOI-2328 b: -0.30…
- Internal temperature T_int =
Uniform prior 50-400 K; posteriors not tabulated
- Per-instrument RV jitter for TOI-2328 b =
FEROS 24.89 +/- 1.49, HARPS 20.76 +/- 4.52, PFS 21.72 +/- 6.11 m/s
- Limb-darkening coefficients q1, q2 per photometric dataset =
Uniform priors; values in Tables 6-9
assumptions (6)
- standard math Keplerian two-body orbit model for the RV signal
- domain assumption Transit signals originate from the target star; no unresolved blended eclipsing binary produces the observed light curve
- ad hoc to paper Two-layer interior structure: 1:1 rock/water core plus H/He envelope with water (GASTLI) or all metals in the core (MESA)
- domain assumption Stellar parameters from zaspe/PARSEC using ATLAS9 model atmospheres and MIST isochrones for the binary blend test
- ad hoc to paper Adopting Teq = 1000 K for TOI-3837 b and TOI-5027 b interior models although fitted Teq are 1182 K and 1056 K
- domain assumption RV variations are not due to stellar activity: no significant peaks in activity indices and no BIS correlation
Cite this review
Pith. "Pith review of Three Warm Jupiters orbiting TOI-6628, TOI-3837, TOI-5027 and one sub-Saturn orbiting TOI-2328." pith.science (2026). https://pith.science/paper/AKK5PJIB
@misc{pith2026241202069,
author = {Pith},
title = {Pith review of: Three Warm Jupiters orbiting TOI-6628, TOI-3837, TOI-5027 and one sub-Saturn orbiting TOI-2328},
year = {2026},
howpublished = {\url{https://pith.science/paper/AKK5PJIB}},
note = {Machine review of arXiv:2412.02069}
}
abstract
We report the discovery and characterization of three new transiting giant planets orbiting TOI-6628, TOI-3837 and TOI-5027, and one new warm sub-Saturn orbiting TOI-2328, whose transits events were detected in the lightcurves of the Transiting Exoplanet Survey Satellite \textbf{(TESS)} space mission. By combining TESS lightcurves with ground-based photometric and spectroscopic follow-up observations we confirm the planetary nature of the observed transits and radial velocity variations. TOI-6628~$b$ has a mass of 0.75$\pm$0.06~$M_\mathrm{J}$, a radius of 0.98$\pm$0.05~$R_J$ and is orbiting a metal-rich star with a period of 18.18424$\pm{0.00001}$ days and an eccentricity of 0.667$\pm0.016$, making it one of the most eccentric orbits of all known warm giants. TOI-3837~$b$ has a mass of 0.59$\pm$0.06~$M_\mathrm{J}$, a radius of 0.96$\pm$0.05~$R_J$ and orbits its host star every 11.88865$\pm$0.00003~days, with a moderate eccentricity of 0.198$^{+0.046}_{-0.058}$. With a mass of 2.01$\pm$0.13~$M_\mathrm{J}$ and a radius of 0.99$^{+0.07}_{-0.12}$ $R_J$, TOI-5027~$b$ orbits its host star in an eccentric orbit with $e$~=~0.395$^{+0.032}_{-0.029}$ every 10.24368$\pm{0.00001}$~days. TOI-2328~$b$ is a Saturn-like planet with a mass of 0.16$\pm$0.02~$M_\mathrm{J}$ and a radius of 0.89$\pm$0.04~$R_J$, orbiting its host star in a nearly circular orbit with $e$~=~0.057$^{+0.046}_{-0.029}$ at an orbital period of 17.10197$\pm{0.00001}$ days. All four planets have orbital periods above 10 days, and our planet interior structure models are consistsent a rocky-icy core with a H/He envelope, providing evidence supporting the core accretion model of planet formation for this kind of planets.
Figures
Figures from the paper (9 more)
Reference graph
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Reviewed August 11, 2026 · model on record in the stance chip above.
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