{"id":"94265532-88a3-4ddb-a63a-67ad5a2bd7aa","arxiv_id":"2509.02666","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"Four new super-Jupiters are confirmed and the subgiant TOI-4138 shows a 4.5-sigma lithium excess attributed to planetary engulfment.","lead":"Astronomers confirmed four giant exoplanets more massive than Jupiter and found unusually strong lithium in one star, a possible sign it swallowed a planet. The lithium excess in TOI-4138 stands out by about 4.5 times the spread of 1,381 similar stars.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Lithium-outlier claim depends on unvalidated TRES-to-GALAH EW scale; a 20-30 mÅ offset would drop TOI-4138 from 4.5σ to ~3.4-2.9σ.","rationale":"The reader's weakest assumption identifies the load-bearing link: an uncalibrated comparison of TRES Li EWs with GALAH DR4 catalog EWs. I agree. The modified Z-score is directly sensitive to a scale offset of the size that can plausibly arise between spectrographs and pipelines; a 20-30 mÅ offset would move TOI-4138 from a 4.5σ outlier to a 2.9-3.4σ excess, which is no longer compelling. The paper's own choice to compare EWs instead of A(Li) makes this bridge unavoidable. This is an addressable concern rather than a fundamental flaw. The four super-Jupiter discoveries stand on robust RV, photometric, and imaging evidence; the TOI-5261 parallax inconsistency in Table 5 is a real but secondary issue. Conditional acceptance remains the right recommendation, with the requested cross-calibration check (or an explicit uncertainty analysis) as a condition. I therefore see no change to the reader's verdict.","tokens_in":32730,"tokens_out":11276,"duration_ms":107283,"concrete_test":"Measure Li I 6707.8 Å EWs with the same five-Gaussian TRES pipeline for 10-20 GALAH DR4 stars that have high-S/N TRES spectra (or obtain short TRES observations of GALAH standard stars) spanning Teff 5500-6500 K, log g 3.5-4.5, and GALAH Li EW 0-150 mÅ. Compare pipeline EWs with the GALAH catalog EWs; if the median residual (TRES minus GALAH) exceeds ~20 mÅ, recompute TOI-4138's modified Z-score after applying that offset to the target value or to the control distribution. If the adjusted significance falls below ~3σ, the engulfment claim is not supported by the present data. Also re-check whether GALAH DR4 Li EW entries include upper limits, since undetected Li in the control sample would bias the median/MAD.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central engulfment interpretation rests on TOI-4138's 120±13 mÅ Li I EW being a 4.47 modified-Z outlier relative to 1,381 GALAH DR4 control stars (§3.2, Table 7, Fig. 4). The significance is not internal to one homogeneous dataset: the target EW comes from 32 co-added TRES spectra (R≈44,000, fixed-width five-Gaussian deblending), while the control EWs come from GALAH DR4, which has different resolution, line-list treatment, and continuum placement. No cross-calibration or overlap sample is presented, and the paper's own justification for comparing raw EWs rather than A(Li) is that conversion choices vary by >10%, making the raw-EW scale comparison the only bridge. With control median≈33 mÅ and MAD≈13 mÅ, applying a 20 mÅ scale offset reduces the modified Z-score from 4.47 to about 3.4; a 30 mÅ offset reduces it to about 2.9. The percentile claim also weakens materially. The four super-Jupiter confirmations are independently supported by RVs, TESS and ground photometry, and speckle imaging; the fragility is specific to the lithium analysis. (A secondary consistency issue: Table 5 lists TOI-5261's Gaia DR3 parallax as -0.20±0.32 mas while §3.1 adopts a Gaussian prior of 2.655±0.061 mas; this should be corrected but does not threaten the engulfment claim.)","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"This manuscript, the second paper in the MEEP survey, reanalyzes the previously known hot Jupiter TOI-4138 b and presents the confirmation and characterization of four new transiting super-Jupiters: TOI-4773 b, TOI-5261 b, TOI-5350 b, and TOI-6420 b. The planet parameters come from global EXOFASTv2 fits combining TESS and ground-based photometry, radial velocities from TRES, CHIRON, and NEID, speckle imaging, and spectral energy distributions, with a common set of priors. The headline result is a strong Li I 6707.8 Å feature in the subgiant TOI-4138 (EW = 120 ± 13 mÅ), which the authors compare with a GALAH DR4 control sample of 1,381 stars and find to be a 4.47-sigma modified-Z outlier, interpreting it as evidence for planetary engulfment. The other three Li detections are weaker and are not claimed as individually significant. TOI-5261 b is highlighted as an 11.49 M_J, e = 0.1585 super-Jupiter orbiting a solar analog, close to the deuterium-burning limit.","tokens_in":33084,"tokens_out":7373,"duration_ms":68132,"significance":"If the results hold, the paper makes a solid contribution: the four super-Jupiters occupy a sparse region of the giant-planet mass-radius diagram and are characterized with a homogeneous methodology, and the paper ships public analysis code and machine-readable radial velocities, which are useful strengths. TOI-5261 b in particular is a noteworthy benchmark object. The lithium analysis has the potential to strengthen the observational case for planetary engulfment, but the core outlier claim currently rests on an unvalidated cross-instrument equivalent-width comparison, and the TOI-5261 astrometry table contains an unexplained inconsistency. If the cross-calibration concern is resolved and the astrometry issue is corrected, the paper would be a valuable addition to the MEEP sample.","major_comments":[{"comment":"The lithium outlier claim compares a TRES-measured EW (R ≈ 44,000; fixed-width five-Gaussian deblending) directly with GALAH DR4 catalog EWs obtained with a different spectrograph and pipeline, and no cross-calibration or overlap sample is presented. Because the control distribution is narrow (median 33 mÅ, MAD 13.1 mÅ), a systematic 20–30 mÅ scale offset would reduce the modified Z-score from 4.47 to roughly 3.4–2.9, materially weakening the outlier claim that underlies the engulfment interpretation. The authors should demonstrate that the two EW scales agree, for example by measuring Li EWs for GALAH stars from spectra reduced in the same way or by quantifying a scale offset from common standard stars, and should propagate the associated systematic uncertainty into the significance.","section":"§3.2, Table 7, Fig. 4"},{"comment":"Table 5 lists TOI-5261's Gaia DR3 parallax as -0.2016 ± 0.3236 mas, while §3.1 and Table 6 adopt a Gaussian prior of 2.655 ± 0.061 mas. The adopted prior is over 8σ discrepant from the catalog value, and the catalog value as printed is unphysical, so either the table entry or the prior needs correction and the source of the prior should be documented. Because this prior effectively sets the distance and stellar radius for TOI-5261, it directly affects the reported planetary radius and density, and the sensitivity of those quantities to the parallax treatment should be quantified.","section":"Table 5 and Table 6"}],"minor_comments":[{"comment":"The caption reports the TOI-4138 Li EW as 121 ± 12 mÅ, while the text, Table 7, and Fig. 2 report 120 ± 13 mÅ; the values should be made consistent.","section":"Fig. 4 caption"},{"comment":"The text refers to 'TOI-4473' where TOI-4773 is meant.","section":"§2.4.2"},{"comment":"Several entries have typographical spacing errors, e.g., '1 .9493±0.0163' and '1 .893±0.014'; these should be corrected.","section":"Table 5"},{"comment":"Table 6 lists TOI-6420's age as 4.4+2.8−20 Gyr, while §4.1 cites 4.2+2.6−1.9 Gyr; the values should be reconciled.","section":"Table 6 and §4.1"},{"comment":"The sentence after the Comove discussion begins with the stray phrase 'TOI-4138 Additionally,' which appears to be a leftover fragment.","section":"§4.1"}],"recommendation":"major_revision","confidential_remarks":"Dear Editor, the paper is a solid survey contribution and the planet discoveries appear robust, with extensive follow-up data and a homogeneous fitting methodology. The lithium story is the headline and is also the fragile part; I would not accept the engulfment claim without a demonstration that the TRES and GALAH Li equivalent-width scales are comparable. The TOI-5261 parallax discrepancy in Table 5 should also be fixed before publication. If these points are addressed, the paper would be suitable for publication."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Paper's real value is the four new super-Jupiters. TOI-4773 b, TOI-5261 b, TOI-5350 b, and TOI-6420 b all get the full treatment: TESS and ground photometry, RVs from multiple spectrographs, speckle imaging to rule out blends, and a SED-consistent EXOFASTv2 fit. TOI-5261 b, the 11.49 M_J eccentric planet around a solar analog, is a genuinely nice addition to a sparse part of the mass-radius diagram. The homogeneous MEEP methodology is a plus, not a gimmick; it makes the sample internally consistent, and the paper is candid about the bimodal TOI-4138 solution and how it differs from Montalto et al.\n\nThe lithium story is the headline, and this is where I part company with the authors' confidence. The 4.47-sigma modified Z-score depends on comparing a 120 mÅ EW measured from co-added TRES spectra against GALAH DR4 catalog EWs. Different resolution, different continuum placement, different deblending. The stress-test note is right: a 20-30 mÅ scale offset drops the significance to roughly 3.4-2.9 sigma. That is not a fatal blow, but it means the engulfment interpretation is plausible rather than secure. The authors justify raw-EW comparison because A(Li) conversions vary, which is fair, but they never show the two EW scales agree. A cross-calibration sample, or at least a systematic error term on the target EW, would fix this. The rest of the lithium analysis is careful: they check youth indicators, search for comoving companions, and honestly discuss nova pollution, so the scientific reasoning is sound even if the statistical framing overcooks it.\n\nMinor but real: Table 5 lists TOI-5261's Gaia DR3 parallax as -0.20±0.32 mas while the fit adopts a prior of 2.655±0.061 mas. That inconsistency should be corrected. There are also a few typos (TOI-4473, malformed table entries), but nothing substantive.\n\nVerdict: the planet confirmations are solid, the lithium claim is a genuinely interesting candidate that needs one more calibration step. This deserves peer review, with a request for the cross-calibration or an explicit caveat on the significance. I'd cite the super-Jupiters without hesitation; I'd cite the lithium claim with a qualifier.","headline":"Four super-Jupiters are solidly confirmed and worth having, but the TOI-4138 lithium excess claim rests on an uncalibrated cross-instrument EW comparison that the stress-test correctly flags.","tokens_in":33721,"tokens_out":1865,"would_cite":true,"duration_ms":19766,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"TOI-4138's host star carries a lithium excess 4.5σ above its peers, which the paper interprets as the signature of a swallowed planet, while four newly confirmed super-Jupiters stretch the survey's sample of massive close-in giants.","keywords":["hot Jupiters","super-Jupiters","lithium-rich stars","planetary engulfment","subgiant stars","exoplanet migration","transit photometry","radial velocities"],"falsifier":"Re-measure TOI-4138's lithium line with an independent high-resolution spectrum, derive the equivalent width using the same five-Gaussian recipe, and rebuild the control-star distribution with identical spectral extraction and line fitting; if the target then falls within about 2 sigma of the control median, the engulfment claim is unsupported.","tokens_in":32582,"feed_emoji":"🪐","tokens_out":8417,"duration_ms":71800,"temperature":0.7,"pith_summary":"This paper argues that TOI-4138, an F-type subgiant hosting the inflated hot Jupiter TOI-4138 b, shows a large photospheric lithium excess: a measured equivalent width of 120 ± 13 mÅ for the lithium doublet at 6707.8 Å, which is a 4.47-sigma outlier against a control sample of 1,381 similar stars. Because the star is old enough that primordial lithium should long ago have been destroyed, and because checks for youth come up negative, the paper concludes that the lithium most plausibly came from the engulfment of a planetary companion. The paper also reports the discovery and characterization of four super-Jupiters, each more than five times Jupiter's mass, one of which, TOI-5261 b, is an eccentric 11.49-Jupiter-mass planet orbiting a solar analog. These systems fill a sparse region of the giant-planet mass-radius diagram and extend a self-consistent sample of hot Jupiters built to test competing migration pathways.","feed_headline":"Swallowed planet leaves a lithium spike in TOI-4138","feed_subtitle":"At 120 mÅ the lithium line is a 4.5σ outlier, pointing to engulfment; four new super-Jupiters join the census.","key_machinery":"The load-bearing measurement is the equivalent width of the Li I 6707.8 Å doublet, extracted from co-added high-resolution spectra (resolving power about 44,000) with a fixed-width five-Gaussian fit that separates the lithium line from blending Fe, CN, V, and Ce features. The statistical significance is then assessed with a modified Z-score against a control sample selected from a large spectroscopic catalog to match each star's color and absolute magnitude within 0.075 magnitudes, after filtering on data-quality flags. The planetary parameters come from a global fitting code that simultaneously models the spectral energy distribution, radial velocities, and transits, with eccentricity and tidal circularization timescales used to interpret migration history.","core_discovery":"The central discovery is that TOI-4138 is a compelling planetary-engulfment candidate. Its lithium I doublet equivalent width of 120 ± 13 mÅ ranks in the 99.86th percentile of a color-magnitude-matched control sample of 1,381 stars (median 33 mÅ, median absolute deviation 13.1 mÅ), giving a modified Z-score of 4.47. The star's evolutionary age—about 5.6 Gyr, with the favored solution at 5.87 Gyr—is far too old for primordial lithium to survive, and checks for youth, including comoving companions, infrared excess, fast rotation, X-ray emission, and a low pre-main-sequence probability, all come back negative. The paper therefore attributes the lithium to ingestion of roughly a Jupiter-mass body, a mechanism predicted to leave a detectable lithium enhancement for up to 1.5 Gyr in this part of parameter space. In the same analysis, four new super-Jupiters are confirmed: TOI-4773 b, TOI-5261 b, TOI-5350 b, and TOI-6420 b, with masses of 5.31, 11.49, 6.59, and 8.2 Jupiter masses. TOI-5261 b's mass approaches the deuterium-burning limit and its eccentricity, 0.1585, is argued to be a relic of high-eccentricity migration.","pith_inferences":["Because the paper compares its measured lithium equivalent width directly with catalog values from a different spectroscopic survey without a cross-calibration step, an independent re-measurement of TOI-4138 and a re-derivation of the control distribution using identical extraction and line-fitting would settle whether the 4.47-sigma excess survives.","If engulfment is the right story, other evolved hot-Jupiter hosts with lithium excesses should exist in rough proportion to how many massive planets get swallowed, so a targeted search for lithium-rich subgiants among planet hosts could quantify the engulfment rate.","The absence of a significant lithium excess in TOI-4773, TOI-5350, and TOI-6420, despite all being planet hosts, suggests the lithium signature depends sharply on stellar mass and timing, and comparing those non-detections with TOI-4138 could map where engulfment lithium remains observable.","TOI-5261 b's near-deuterium-burning mass invites a follow-up test of whether its atmosphere or spin-orbit alignment carries remnants of its formation, a prediction that specific observations could check."],"forward_implications":["If TOI-4138's lithium really records an engulfment, its surviving hot Jupiter becomes a benchmark for post-engulfment planetary evolution, and the system offers a place to test dynamical scenarios in which a migrating giant planet scatters or drags companions into its star.","The four super-Jupiters occupy a sparsely populated region of the mass-radius diagram above five Jupiter masses, where core-accretion theory predicts fewer outcomes, so their measured radii and densities add constraints to giant-planet structure and inflation.","TOI-5261 b, at 11.49 Jupiter masses with significant eccentricity, sits near the deuterium-burning boundary and may help distinguish high-eccentricity migration from disk migration for massive close-in planets.","Each system increases the size of the survey's homogeneous, magnitude-limited hot-Jupiter sample, bringing closer a statistical test of how often each migration pathway operates.","The roughly 100 m/s offset between the two observing seasons of TOI-4138 radial velocities hints at a long-period companion whose confirmation would connect the engulfment and migration narrative."],"supporting_citations":[{"why":"Discovered TOI-4138 b and established its low density and evolved-star context; the reanalysis compares its new solution against this discovery work.","marker":"Montalto et al. (2022)"},{"why":"First paper in the survey series; supplies the fitting conventions, priors, and follow-up methodology used throughout this analysis.","marker":"Schulte et al. (2024)"},{"why":"Describes the global fitting code that simultaneously models the spectral energy distribution, radial velocities, and transits to produce the stellar and planetary parameters.","marker":"Eastman et al. (2019)"},{"why":"Provides the large spectroscopic catalog from which the 1,381-star control sample is drawn for the lithium outlier analysis.","marker":"Buder et al. (2024)"},{"why":"Predicts that a gas-giant engulfment produces a statistically significant, long-lived lithium enhancement for stars like TOI-4138, forming the interpretive anchor for the engulfment claim.","marker":"Soares-Furtado et al. (2021)"},{"why":"Argues that solar-metallicity stars of roughly 1.1 to 1.2 solar masses have the largest and longest-lived chemical signatures of planet engulfment, matching TOI-4138's parameters.","marker":"Behmard et al. (2023)"},{"why":"Defines the modified Z-score statistic used to declare TOI-4138 a 4.47-sigma lithium outlier.","marker":"Iglewicz & Hoaglin (1993)"},{"why":"Supplies the lithium-based age estimator used to show that TOI-4138's strong lithium implies an implausibly young age, ruling out youth as the explanation.","marker":"Jeffries et al. (2023)"},{"why":"Provides the five-Gaussian lithium equivalent-width measurement methodology that the paper adapts for its co-added spectra.","marker":"Wang et al. (2024)"}],"fun_headline_variants":["Star's lithium spike signals a swallowed planet","TOI-4138 ate a Jupiter, leaving a lithium bloom","Four super-Jupiters plus a planet-eating star","Engulfment clue: lithium-rich star in hot Jupiter survey","Devoured planet leaves lithium in TOI-4138"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The engulfment conclusion rests on comparing a lithium equivalent width measured from the paper's own spectra against catalog values from a different survey without a cross-calibration step, so a small systematic offset between the two measurement scales could turn the 4.5-sigma outlier into an ordinary star.","fun_headline_variants_meta":{"raw":{"variants":["Star's lithium spike signals a swallowed planet","TOI-4138 ate a Jupiter, leaving a lithium bloom","Four super-Jupiters plus a planet-eating star","Engulfment clue: lithium-rich star in hot Jupiter survey","Devoured planet leaves lithium in TOI-4138"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000764,"raw_usage":{"total_tokens":3513,"prompt_tokens":1189,"completion_tokens":2324,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":805,"completion_tokens_details":{"reasoning_tokens":2244}},"tokens_in":805,"tokens_out":2324,"duration_ms":15919,"temperature":1.0,"reasoning_tokens":2244,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-15T16:36:43.723002+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Re-measure TOI-4138's lithium line with an independent high-resolution spectrum, derive the equivalent width using the same five-Gaussian recipe, and rebuild the control-star distribution with identical spectral extraction and line fitting; if the target then falls within about 2 sigma of the control median, the engulfment claim is unsupported.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Discovered TOI-4138 b and established its low density and evolved-star context; the reanalysis compares its new solution against this discovery work."}],"review_version":2}