{"id":"13248528-7788-48a7-b022-063bbdaaae80","arxiv_id":"2411.10520","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":4,"one_line_summary":"In luminous red giants, the large frequency separation scaling relation contributes more than the frequency of maximum power relation to the observed breakdown of asteroseismic radii, and theoretical correction factors tested here are too small to explain the inflation.","lead":"This paper tests which half of the standard asteroseismology recipe, the frequency spacing or the oscillation frequency of peak power, breaks down for very large red giant stars. The authors find the spacing relation is the bigger problem, but the correction factors they test cannot explain the observed 9% radius inflation.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"High-α sample is cleaned with 5σ cuts on the same single-parameter scaling-relation masses used to measure the Δν vs νmax trend; this selection bias can create the luminous-giant offset, so the central attribution is not secure.","rationale":"The paper has real strengths: the FΔν model comparison is direct, the null result that mixing-length calibration and mode selection shift luminous-giant radii by only 1-3% is a useful negative result, and the data are publicly hosted. But the headline claim is the ranking of Δν vs νmax, and that ranking is only as good as the high-α benchmark. The reader's conditional verdict already captures that the high-α result is not 3σ in metallicity bins; my concern is more pointed: the sample selection itself is contaminated by the dependent variable. The 5σ mass cut is applied to the single-parameter scaling relation masses before the very comparison that defines the outcome. This is not an exotic assumption but a standard selection-bias trap, and it is directly testable by re-running the analysis without the cut or with varied cuts. If the trend persists under all reasonable cut choices, then the concern is resolved and the conditional accept stands. If it does not, the abstract's central claim would need to be weakened. I therefore do not change the verdict: CONDITIONAL remains appropriate, but the condition should explicitly include the mass-cut robustness check described above.","tokens_in":30491,"tokens_out":9363,"duration_ms":93115,"concrete_test":"Recompute the high-α rolling medians and the significance of the Δν-only vs νmax-only mass offsets in Figs. 5-6 after removing the 5σ cut on the single-parameter scaling relation masses (Eqs. 6 and 7), retaining only the APOKASC3 catalog mass cut (or no mass cut). Repeat with one-sided, two-sided, and thresholds 3σ/5σ/7σ. If the Δν-only offset in the 30-50 R⊙ range or its downturn above 50 R⊙ weakens or vanishes under any of these variants, the attribution of the breakdown to Δν is a selection artifact rather than a scaling-relation failure.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central empirical claim that Δν, not νmax, drives the luminous-giant breakdown rests on the high-α sequence analysis (Sec. 3.2.2, Figs. 5-6) plus five luminous cluster stars. But the high-α sample is selected in Sec. 2.4.4 by a '5σ mass cut on the APOKASC3 catalog mass and the single-parameter scaling relation masses' — the latter being precisely the masses computed from Eqs. 6 and 7 that are later compared, as a function of radius, with the sequence's median mass. This is a selection on the outcome variable. At fixed radius, the single-parameter mass estimates have large scatter, especially in the luminous regime (νmax ≲ 5 μHz; pipeline scatter already ~2-3% in Δν, Sec. 4.3.2). A one-sided upper cut removes the most over-massive stars in each bin; in the small-N, high-error tail above ~50 R⊙ it can depress the rolling median and create the downturn from over-massive to under-massive stars that the paper interprets as the Δν 'curvature' mirroring the full scaling relation. Because the same cut is applied to the Δν-only masses but the test quantity is the difference between two relations, the νmax-only and Δν-only trends can differ as an artifact of how the cut interacts with each relation's power of R (Eq. 6 has R^2; Eq. 7 has R^3). No analysis or caveat in the paper quantifies this. The clusters provide only 4+1 luminous giants, so the high-α result is the only statistically meaningful test of the attribution; if the mass-cut bias is responsible for the offset, the abstract's ranking of Δν over νmax is unsupported. Note also that the reference 'median mass of the high-α sequence' is measured on stars with R<30 R⊙; if the luminous subsample is genuinely more massive (age spread ±0.9 Gyr, Sec. 2.4.4), both single-parameter scales would be compared to too low a reference, though this alone acts similarly on both relations.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper tests the asteroseismic scaling relations for luminous red giants by separating the contributions of νmax and Δν. It uses parallactic radii from Gaia and independent masses from the open clusters NGC 6791 and NGC 6819 and from the Milky Way's high-α sequence as benchmarks. The authors derive single-parameter scaling relations for νmax and Δν and compare the resulting masses with the benchmarks as a function of radius. They find that the Δν-only relation shows larger, radius-dependent deviations than the νmax-only relation, and they interpret this as evidence that the Δν scaling relation is the main contributor to the previously reported breakdown of the joint scaling relations in luminous giants. They then compute model-based FΔν corrections using MESA+GYRE grids and test the effects of mixing-length calibration and of measuring Δν from all modes versus an observationally motivated subset of modes. These model changes alter the inferred radii by only about 1–3%, which is too small to explain the ≈9% inflated seismic radii. The paper concludes that the theoretical FΔν corrections, at least within the tested model treatments, cannot resolve the luminous-giant discrepancy.","tokens_in":30814,"tokens_out":7343,"duration_ms":72605,"significance":"If the central attribution is correct, the paper identifies the Δν-to-mean-density mapping as the weak link in the asteroseismic scaling relations for luminous giants, which would directly affect Galactic archaeology and planned single-parameter asteroseismic programs such as the Roman Galactic Bulge Time Domain Survey. The modeling null result is also useful: it shows that two plausible model treatments (mixing-length calibration and mode selection) do not resolve the discrepancy, narrowing the search space. The paper is commendably transparent about its limitations: it states that the metallicity-binned Δν deviations are not at 3σ significance and that the cluster luminous-giant sample is only four stars in NGC 6819 and one in NGC 6791. The data and MESA/GYRE inlists are publicly available, which is a strength. The main empirical claim is therefore suggestive but not yet secure; the selection effects in the high-α sample and the small cluster sample need to be quantitatively addressed before the attribution can be regarded as established.","major_comments":[{"comment":"The high-α sample is cleaned with a 5σ mass cut applied to the APOKASC3 catalog mass and to the single-parameter scaling-relation masses computed from Eqs. (6) and (7). Because the subsequent analysis is precisely the radius-dependent behavior of those same single-parameter masses, this constitutes a selection on the outcome variable. At fixed radius the single-parameter masses scatter widely, and in the luminous regime the 2–3% inter-pipeline scatter in Δν (Sec. 4.3.2) enlarges that scatter. A one-sided upper cut removes the most over-massive stars in each bin; in the small-N tail above ≈50 R⊙, where the errors are largest, this can depress the rolling median and create the downturn from over-massive to under-massive stars that is interpreted as the Δν curvature. The Δν-only mass scales as R^3 while the νmax-only mass scales as R^2 (Eqs. 6 and 7), so the same cut can affect the two trends differently and artificially produce the relative offset between them. The paper does not quantify this selection effect. Please add a quantitative test—for example, apply the same mass-cut and rolling-median procedure to synthetic data with no true breakdown and show that the observed Δν-versus-νmax difference is not reproduced; if it is reproduced, the central attribution is not secure.","section":"Sec. 2.4.4 and Sec. 3.2.2, Eqs. (6)-(7), Figs. 5-6"},{"comment":"The paper's internal significance statements are weaker than the abstract's claim. Section 3.2.2 states that the metallicity-binned Δν deviations are 'not at a 3σ level of significance,' and Section 3.2.1 reports only four luminous giants in NGC 6819 and one in NGC 6791. Despite this, the abstract asserts that 'the Δν-scaling relation contributes to the observed breakdown in luminous giants more than the νmax relation.' The cluster luminous-giant masses for the single-parameter relations are statistically consistent with the isochrone mass in both clusters (Tables 3 and 4, 'Luminous RGB' rows). Please either soften the abstract to match the stated significance (e.g., 'tentatively indicates' or 'we find suggestive evidence'), or add a combined statistical test across the high-α bins and the cluster stars that accounts for the selection effect raised in the first major comment. The current wording overstates the evidential weight of the analysis.","section":"Sec. 3.2.2 and Sec. 3.2.1, Tables 3-4"},{"comment":"The high-α 'pseudo-cluster' benchmark mass (median 1.04 M⊙ for R < 30 R⊙) is used as the seismic-independent reference, but its provenance is not explicitly stated. If this median mass is derived from APOKASC3 catalog masses, then it is not independent of the scaling relations being tested; a global zero-point error in the APOKASC3 calibration would be hidden, and only the radius-dependent trend would be meaningful. Please clarify how the benchmark mass is computed (isochrones, APOKASC3, or other) and test the sensitivity of the Figs. 5 and 6 trends to the assumed benchmark mass and to its possible variation with radius. This is important because the central attribution depends on the benchmark being a valid single-mass reference across the entire giant branch.","section":"Sec. 2.4.4 and Sec. 3.2.2"}],"minor_comments":[{"comment":"The text says NGC 6791 has a turnoff age of '≈ 8 Myr'; this should read '≈ 8 Gyr' to be consistent with the adopted isochrone age of 8.3 ± 0.3 Gyr in Sec. 2.4.3.","section":"Sec. 2.4.2"},{"comment":"Equation (6) shows the νmax-only mass without any Fνmax term, while the surrounding text and the middle panel of Fig. 4 indicate that a constant Fνmax is applied. Please clarify whether Eq. (6) should include Fνmax and, if so, where it enters; this affects the absolute mass scale, though not the radius-dependent curvature.","section":"Eq. (6) and Sec. 3, Fig. 4"},{"comment":"The y-axis labels are rendered as 'max' instead of 'νmax'; the symbols are missing in several axis labels and captions throughout the paper (e.g., 'Rseis', 'Mhigh'). Please ensure the math mode renders correctly.","section":"Figs. 5 and 6"},{"comment":"The caption contains the typo 'Asteroseiemic'; should be 'Asteroseismic'.","section":"Table 1 caption"},{"comment":"The bullet 'astreroseismic scaling relationships' contains a typo; should be 'asteroseismic'.","section":"Sec. 5, bullet list"},{"comment":"The sentence 'Using a Kolmogorov-Smirnov (KS) tests we confirm...' has a subject-verb agreement error; should be 'Using Kolmogorov-Smirnov (KS) tests, we confirm...'.","section":"Sec. 3.2.2, KS test sentence"}],"recommendation":"major_revision","confidential_remarks":"The paper is transparent about its limitations and provides public data and inlists, which is commendable. However, the abstract's central claim ('we find evidence that the Δν-scaling relation contributes more than the νmax relation') is not supported by the stated significance levels in the body, and the high-α selection effect could undermine the attribution entirely. The first major comment (the 5σ mass-cut selection on the outcome variable) is the load-bearing issue; without a quantitative demonstration that the selection does not create the observed trend, the paper's main conclusion is not secure. The modeling work is sound and the null result is publishable, but the framing needs to match the evidence. I would recommend major revision rather than rejection because the selection-bias concern is testable within the manuscript's scope, and the authors have already assembled the necessary data and machinery to address it."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"This paper deserves a serious referee. It does something new: instead of testing the joint asteroseismic scaling relation, it separates νmax and Δν using Gaia DR3 parallactic radii and the high-α sequence as a pseudo-cluster, and it compares all-modes versus observationally-motivated mode subsets for FΔν. The modeling section is the strongest piece. The conclusion that FΔν is insensitive to mixing length calibration, and that the two mode-selection techniques differ by only 1–3% in radius, is well supported by direct model comparisons. That is a useful negative result: the tested theoretical treatments cannot explain the inflated seismic radii in luminous giants.\n\nThe soft spot is the empirical attribution. The abstract says the Δν scaling relation contributes more than νmax, but the paper itself admits the metallicity-binned high-α deviations are not at 3σ significance, and the luminous cluster sample is four stars in NGC 6819 plus one in NGC 6791. The high-α analysis is therefore the only statistically meaningful test, and here the stress-test concern lands: the sample is cleaned with 5σ cuts on the same single-parameter masses (Eqs. 6 and 7) that are later compared as a function of radius. That is selection on the outcome variable. In the luminous tail, where the number of stars is small and measurement scatter is large, a one-sided upper cut can depress the rolling median and create a downturn that mimics the Δν curvature. Because the two relations scale with different powers of R, the cut can affect them differently. The paper uses median statistics, which helps, but it does not quantify the bias. This should be addressed before the Δν-over-νmax claim is taken as definitive.\n\nOther issues are minor but worth fixing: the overshoot parameters are inconsistent between the text (f=0.0014, f0=0.004) and the Appendix inlist (0.014 and 0.004); the models lack uncertainty bands; and the mixing length calibration is fit on stars with R≤20 R⊙ but applied to luminous giants. None of these invalidate the modeling results.\n\nOverall: the paper is careful, honest about its limitations, and the modeling negative result is solid. The empirical ranking of Δν over νmax is suggestive, not proven. I would cite it, and I would send it to peer review with a request for a quantitative treatment of the selection bias and a softened abstract.","headline":"A careful, genuinely new decomposition of the luminous-giant scaling breakdown, but the central Δν-vs-νmax ranking rests on small samples and a selection procedure that could bias the trend; the modeling negative result is the strongest part.","tokens_in":31481,"tokens_out":1959,"would_cite":true,"duration_ms":21904,"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":"The paper argues that the breakdown of asteroseismic scaling relations in luminous red giants is driven mainly by the large-frequency-separation mapping to mean density, not by the frequency of maximum power scaling.","keywords":["asteroseismology","red giants","scaling relations","luminous giant branch","large frequency separation","frequency of maximum power","stellar radii","open clusters"],"falsifier":"A luminosity-selected sample of luminous giants in additional open clusters, or with eclipsing-binary masses, comparing $\\nu_{\\max}$-only and $\\Delta\\nu$-only masses would settle the attribution: if the $\\Delta\\nu$-only masses no longer track the inflated seismic radii while the $\\nu_{\\max}$-only masses do, the breakdown would move to the $\\nu_{\\max}$ side.","tokens_in":30245,"feed_emoji":"🔭","tokens_out":5737,"duration_ms":51472,"temperature":0.7,"pith_summary":"The asteroseismic scaling relations that turn measured oscillation frequencies into stellar masses and radii work well on the lower red giant branch and red clump, but they break down for luminous red giants, where seismic radii come out about 9% larger than parallactic radii. The paper isolates the two ingredients of the breakdown: the scaling that ties the large frequency separation $\\Delta\\nu$ to mean density and the scaling that ties the frequency of maximum power $\\nu_{\\max}$ to surface gravity. Using open cluster stars and the Milky Way's high-$\\alpha$ sequence as independent mass benchmarks, it finds that the $\\Delta\\nu$ relation produces the more discrepant masses in the luminous giant regime, so the $\\Delta\\nu$ mapping is the larger contributor to the inflated radii. It then shows that two ways of computing the $\\Delta\\nu$ correction factor $F_{\\Delta\\nu}$ from stellar models, using all synthetic modes versus an observationally motivated subset with or without mixing-length calibration, shift the inferred radii by only 1 to 3 percent, too little to explain the breakdown.","feed_headline":"Δν scaling, not νmax, breaks down in luminous red giants","feed_subtitle":"Isolating the two scalings pins the 9% radius inflation on the Δν–mean density mapping.","key_machinery":"The argument runs through the single-parameter scaling relations, which let each observed asteroseismic quantity be tested separately against independent masses and radii. The $\\nu_{\\max}$-only relation is $$\\frac{M_*}{M_\\odot} = \\frac{\\nu_{\\max}}{\\nu_{\\max,\\odot}} \\left(\\frac{R_{\\rm Gaia}}{R_\\odot}\\right)^2 \\left(\\frac{T_{\\rm eff}}{T_{\\rm eff,\\odot}}\\right)^{1/2},$$ and the $\\Delta\\nu$-only relation is $$\\frac{M_*}{M_\\odot} = \\left(\\frac{F_{\\$\\Delta$\\nu}\\,\\$\\Delta$\\nu}{\\$\\Delta$\\nu_\\odot}\\right)^2 \\left(\\frac{R_{\\rm Gaia}}{R_\\odot}\\right)^3,$$ where $F_{\\Delta\\nu}$ is the correction factor mapping the observed large frequency separation to mean density through $(F_{\\Delta\\nu}\\Delta\\nu_{\\rm obs})/\\Delta\\nu_\\odot = ((M/M_\\odot)/(R/R_\\odot)^3)^{1/2}$. The benchmarks are the open clusters NGC 6819 and NGC 6791, with isochronal and eclipsing-binary masses, and the high-$\\alpha$ sequence as a quasi-coeval population of median mass near $1.04\\,M_\\odot$. The paper also builds MESA stellar models and GYRE non-adiabatic synthetic frequency spectra to test how measuring $\\Delta\\nu$ from all modes versus an observationally accessible subset, with and without a metallicity-dependent mixing-length calibration, changes $F_{\\Delta\\nu}$ and therefore the inferred radius.","core_discovery":"The central claim is that in luminous red giants, conventionally stars with seismic radii above about $30\\,R_\\odot$, the observed inflation of asteroseismic radii relative to Gaia parallactic radii originates primarily from the $\\Delta\\nu$-to-mean-density side of the joint scaling relations. The evidence comes from splitting the joint relations into a $\\nu_{\\max}$-only mass relation and a $\\Delta\\nu$-only mass relation, applied to open cluster stars and the high-$\\alpha$ sequence used as a pseudo-cluster of known mean mass. The $\\nu_{\\max}$-only relation stays consistent with the high-$\\alpha$ median mass across the giant branch, while the $\\Delta\\nu$-only relation runs over-massive in the 30 to 50 solar radius regime, mirroring the curvature of the joint scaling relations. The paper further claims that theoretical corrections to the $\\Delta\\nu$ mapping, through either mode selection or mixing-length calibration, alter inferred radii by only about 1 to 3 percent, which cannot account for the roughly 9 percent radius inflation, and that the $F_{\\Delta\\nu}$ correction is insensitive to the adopted mixing length calibrated to observed effective temperatures.","pith_inferences":["If the $\\Delta\\nu$ attribution is correct, then surface-effect corrections applied to individual oscillation frequencies, which mainly act on the frequency pattern, would not be expected to cure the luminous-giant radius inflation either; the cause would more likely live in how luminous-giant structure maps onto the asymptotic relation.","A direct extension would be to measure $F_{\\Delta\\nu}$ empirically for luminous giants using asteroseismic radii anchored to eclipsing binaries at large radius, which would test whether the correction factor is radius dependent rather than merely method dependent.","The insensitivity of $F_{\\Delta\\nu}$ to mixing length suggests that the breakdown is not a convective-efficiency calibration problem, leaving non-adiabatic and atmospheric modeling, or missing physics such as magnetic fields or rotation, as the more promising explanations.","The small number of luminous cluster giants, four in NGC 6819 and one in NGC 6791, means that a larger cluster sample or a dedicated high-$\\alpha$ sample with independent radii could sharpen the claim that $\\Delta\\nu$ dominates over $\\nu_{\\max}$."],"forward_implications":["The $\\nu_{\\max}$-only scaling relation is a reliable mass and radius estimator on the lower giant branch, so surveys that rely on $\\nu_{\\max}$ alone can proceed with caution there, but they should be calibrated separately before being extended to luminous giants.","The $\\Delta\\nu$-only relation is the part of the scaling relations that needs re-examination if the luminous-giant breakdown is to be fixed.","Changing the way $\\Delta\\nu$ is measured in theoretical spectra, or calibrating mixing length to observed effective temperatures, will not by itself remove the discrepancy in luminous giant radii.","Radius calibrations applied through a $F_{\\nu_{\\max}}$ term do not necessarily correct the mass scale, meaning that calibrated radii and calibrated masses are not interchangeable tests of the scaling relations.","Future population studies using only one asteroseismic parameter in the luminous giant regime should carry an extra systematic uncertainty until the physical source of the $\\Delta\\nu$ failure is identified."],"supporting_citations":[{"why":"Established the observed breakdown, the roughly 9% inflation of seismic radii relative to parallactic radii in luminous giants, which this paper sets out to explain.","marker":"Zinn et al. (2019b)"},{"why":"Provides the APOKASC3 catalog with uniform Kepler asteroseismic parameters, APOGEE spectroscopy, and the calibrated radius scale used throughout the analysis.","marker":"Pinsonneault et al. (2024)"},{"why":"Defined the high-$\\alpha$ sequence as a pseudo-cluster of thick disk stars with a sharply peaked mass distribution, the key independent mass benchmark.","marker":"Miglio et al. (2021)"},{"why":"Introduced the $\\nu_{\\max}$ and $\\Delta\\nu$ scaling relations that the paper tests separately.","marker":"Kjeldsen & Bedding (1995)"},{"why":"Introduced the $F_{\\Delta\\nu}$ correction factor that maps observed frequency spacings to mean density, the central theoretical object of the modeling section.","marker":"White et al. (2011a)"},{"why":"Supplied the metallicity-dependent mixing length relation used to calibrate the MESA models against observed effective temperatures.","marker":"Tayar et al. (2017)"},{"why":"Provided the low-frequency $\\nu_{\\max}$ measurement method and universal red giant oscillation pattern used to remeasure the luminous giant in NGC 6791.","marker":"Mosser et al. (2013)"},{"why":"Gives an independent asteroseismic mass for NGC 6819, used as a comparison point for the cluster scaling-relation masses.","marker":"Handberg et al. (2017)"}],"fun_headline_variants":["Δν scaling, not νmax, breaks down in luminous red giants","Luminous red giants: Δν mapping inflates radii, νmax does not","Breakdown in giant star radii traced to Δν scaling","νmax scaling holds, Δν scaling breaks for luminous giants","Δν scaling errors inflate radii in luminous red giants"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The high-$\\alpha$ sequence is treated as a pseudo-cluster with a single well-defined mass, median $1.04\\,M_\\odot$ for radii below $30\\,R_\\odot$, and a narrow age spread, and the 5-$\\sigma$ mass cuts used to clean it are assumed not to bias the radius-dependent mass trend.","fun_headline_variants_meta":{"raw":{"variants":["Δν scaling, not νmax, breaks down in luminous red giants","Luminous red giants: Δν mapping inflates radii, νmax does not","Breakdown in giant star radii traced to Δν scaling","νmax scaling holds, Δν scaling breaks for luminous giants","Δν scaling errors inflate radii in luminous red giants"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000316,"raw_usage":{"total_tokens":1865,"prompt_tokens":1094,"completion_tokens":771,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":710,"completion_tokens_details":{"reasoning_tokens":681}},"tokens_in":710,"tokens_out":771,"duration_ms":6707,"temperature":1.0,"reasoning_tokens":681,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-12T19:36:49.473084+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A luminosity-selected sample of luminous giants in additional open clusters, or with eclipsing-binary masses, comparing $\\nu_{\\max}$-only and $\\Delta\\nu$-only masses would settle the attribution: if the $\\Delta\\nu$-only masses no longer track the inflated seismic radii while the $\\nu_{\\max}$-only masses do, the breakdown would move to the $\\nu_{\\max}$ side.","supporting_citations":[{"cited_title":"H., Zinn , J","cited_arxiv_id":null,"evidence_quote":"Provides the APOKASC3 catalog with uniform Kepler asteroseismic parameters, APOGEE spectroscopy, and the calibrated radius scale used throughout the analysis."},{"cited_title":"A., Belkacem , K., et al","cited_arxiv_id":null,"evidence_quote":"Provided the low-frequency $\\nu_{\\max}$ measurement method and universal red giant oscillation pattern used to remeasure the luminous giant in NGC 6791."}],"review_version":1}