{"id":"7ff61889-9a1f-48dd-a604-e2063c8db621","arxiv_id":"2506.08078","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":0,"one_line_summary":"The EGPM survey measures a 1.9% occurrence rate for giant planets within 2.5 AU around 20-200 Myr G/K dwarfs, consistent with but lower than the field-age rate, and excludes strong decay over time.","lead":"A four-year near-infrared radial velocity survey of 85 young Sun-like stars finds that giant planets inside the water ice line are rare at ages 20-200 million years, with an occurrence rate of about 1.9%. The rate is lower than, but still consistent with, the older field-star rate of 6.5%, leaving the evolution of giant planet migration an open question.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The age-evolution interpretation assumes the young YMG sample and Johnson et al. (2010) field sample have matching metallicity distributions; the paper asserts this match but provides no [Fe/H] data, so the lower 1.9% rate could be a metallicity effect rather than a true age trend.","rationale":"The reader's weakest_assumption identified that the young and old samples may differ in birth environment, which is a real confound. I sharpen this to a specific, testable physical parameter: metallicity. The paper explicitly claims the samples are matched to avoid metallicity biases, but provides no metallicity measurements for the 85 targets. Since Johnson et al. (2010) selected [Fe/H] = 0 dex and giant planet occurrence is known to rise steeply with metallicity, an unverified metallicity mismatch could fully account for the lower young-star occurrence rate without any age evolution. This does not undermine the internal validity of the occurrence-rate measurement itself, which appears carefully computed with transparent completeness and uncertainty propagation. It does, however, weaken the central evolutionary conclusion. Because the paper already received a CONDITIONAL verdict from the reader, and this concern reinforces the need for additional verification rather than overturning the measurement, the verdict should remain unchanged. A concrete check on the metallicity distributions would settle whether this concern lands.","tokens_in":52682,"tokens_out":14720,"duration_ms":190170,"concrete_test":"Measure or compile [Fe/H] for all 85 EGPM targets from the existing HPF spectra or literature, and compare the distribution to the Johnson et al. (2010) solar-metallicity sample. If the EGPM median [Fe/H] is significantly below 0 dex, use the Fischer & Valenti (2005) occurrence-metallicity relation to predict the expected field-age rate at that metallicity; if the prediction is consistent with 1.9%, the claimed age increase is not supported.","verdict_should_be":"UNCHANGED","load_bearing_attack":"Section 5.3 states that the EGPM sample was 'assembled to match the stellar parameters of targets from Johnson et al. (2010)' and that this avoids 'known correlations in the occurrence rate of giant planets, such as with stellar metallicity and mass.' However, Table 5 lists no [Fe/H] for the 85 targets, and no comparison of the metallicity distributions is presented. Johnson et al. (2010) restricted their field sample to [Fe/H] = 0 dex, and giant planet occurrence scales steeply with metallicity (e.g., Fischer & Valenti 2005). If the young moving group stars are systematically subsolar, the observed difference between 1.9% and 6.5% could be explained entirely by metallicity, independent of age. The birth-environment caveat in Section 5.3 is a special case of this: metallicity is set by the formation environment. The paper's central evolutionary claim therefore rests on an asserted but unverified sample match. This is not an internal inconsistency in the rate measurement, but it is a load-bearing missing check on the interpretation.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"This paper presents the statistical results of the Epoch of Giant Planet Migration (EGPM) radial-velocity survey: 85 young (20-200 Myr) G and K dwarfs observed over about 4 years with the HPF spectrograph. The survey detects one young hot Jupiter candidate, HS Psc b, and uses per-star detection-limit completeness maps to infer a giant-planet occurrence rate of 1.9^{+2.6}_{-1.4}% for 0.3-13 M_Jup companions within 2.5 AU, together with a hot-Jupiter rate of 1.5^{+2.2}_{-1.1}% and a 95% upper limit of <3.6% for brown dwarfs within 5000 d. The authors compare the 1.9% rate with the 6.5±0.7% field-age rate from Johnson et al. (2010), model the evolution with a two-point power law, and conclude that the data favor an increase in giant-planet frequency with age while not ruling out a constant rate. The paper also includes a multi-instrument reanalysis of HD 130322 b and a detailed account of binary and field-age contaminants removed from the sample.","tokens_in":52896,"tokens_out":9207,"duration_ms":112658,"significance":"If the central rate holds, this is one of the most direct RV-based constraints on giant-planet demographics at intermediate ages and provides a valuable benchmark for migration theories: the comparison between young and field populations bears directly on whether close-in giants arrive early via disk migration or late via dynamical processes. The survey design is a genuine strength: a 4-year NIR RV campaign on young active stars, a clearly defined statistical sample, standard completeness methodology, and honestly quoted uncertainties. The detection of HS Psc b and the successful recovery of HD 130322 b with HPF demonstrate the survey's sensitivity. The paper is appropriately cautious in most of the body, but the central evolutionary interpretation is currently limited by a single detection and by an unverified assumption that the young and field samples are matched in metallicity; these issues, rather than the rate measurement itself, are what prevent the conclusions from being fully load-bearing.","major_comments":[{"comment":"The abstract states that 'A decaying planet occurrence rate is, however, strongly excluded,' but this is stronger than the body supports. Section 5.1 explicitly says a constant frequency cannot be confidently excluded, and the quantitative statement is only that a young-age rate 1.3× and 1.9× the field-age rate is excluded at 95% and 99% confidence, respectively. This excludes decay factors of roughly 30% or more, not decay in general; mild decay is statistically indistinguishable from a constant rate given the stated posterior widths. Please revise the abstract and Section 6 to characterize the exclusion as a function of decay factor and remove the unqualified 'strongly excluded' claim.","section":"Abstract and §5.1"},{"comment":"The evolutionary interpretation rests on comparing the 1.9% young rate with the 6.5% field rate of Johnson et al. (2010), and Section 5.3 asserts that the EGPM sample was 'assembled to match the stellar parameters of targets from Johnson et al. (2010)' to avoid known correlations with stellar metallicity and mass. However, Table 5 contains no [Fe/H] measurements, and no comparison of the metallicity distributions of the two samples is presented. Johnson et al. (2010) deliberately restricted their field sample to [Fe/H] = 0 dex, and giant-planet occurrence is a steep function of metallicity (Fischer & Valenti 2005). If the young moving-group stars are systematically subsolar, the entire difference between 1.9% and 6.5% could reflect metallicity rather than age evolution. The birth-environment caveat in Section 5.3 is a special case of this concern. Please provide [Fe/H] values for the 85 targets or a literature-based demonstration that the two samples have matched metallicity distributions, and discuss how plausible metallicity offsets would shift the inferred power-law index alpha.","section":"§5.3 and Table 5"},{"comment":"The abstract credits the survey with 'realistic injection-recovery tests,' but Section 4.5 does not describe an injection-recovery procedure. The text describes fitting circular Keplerian orbits with radvel over a grid of orbital periods and adopting the maximum K that matches the observed RVs as a detection threshold; there is no description of injecting synthetic planet signals into the data and recovering them, and no explicit treatment of how stellar activity jitter is folded into those limits. Since the occurrence rate in Equation (2) is directly normalized by the completeness function C(P,K), the completeness method is load-bearing for the 1.9% result. Please clarify whether injections were actually performed and describe them if so, or recast the abstract and Section 4.5 as maximum-K detection-limit completeness.","section":"§4.5 and Abstract"},{"comment":"HS Psc b is consistently described as a 'young giant planet candidate' in Section 4.4.1, but it is treated as a confirmed detection in the occurrence-rate calculation in Section 4.6 and in Table 2. Because the central 1.9% rate and the age-evolution conclusions are driven entirely by this one system, the manuscript should either clarify the confirmation status with an explicit reference to the evidence in Tran et al. (2024) or provide a sensitivity test in which HS Psc b is treated as a non-detection. Without this, the reader cannot assess how much of the conclusion depends on an unconfirmed candidate.","section":"§4.4.1, §4.6, Table 2"}],"minor_comments":[{"comment":"The first sentence of Appendix D reads 'Throughout the EPGM survey'; the program name should be EGPM.","section":"Appendix D"},{"comment":"The sentence 'but less in known about trends of RV jitter in the NIR' contains a typo; it should read 'but less is known'.","section":"Section 3"},{"comment":"The caption reads '91% our targets have at least 7 epochs'; '91%' should be followed by 'of'.","section":"Figure 1 caption"},{"comment":"The summary bullet says the survey obtained 2666 spectra, but Section 2.2 reports 2654 spectra for 104 stars; please reconcile the two numbers.","section":"Section 6"},{"comment":"The table footnote symbols (b, c, d, e) are defined, but the note for the brown-dwarf row citing Takarada et al. (2020) appears to use the same symbol as the hot-Jupiter row; please verify the footnote assignments.","section":"Table 2 notes"}],"recommendation":"major_revision","confidential_remarks":"The rate measurement itself is competently done and the paper is a useful contribution, but the central age-evolution claim currently depends on two unverified premises: that the young and field samples are metallicity-matched, and that the single candidate detection is securely planetary. Neither is fatal to the survey, but both need to be addressed before the evolutionary interpretation can be accepted. The stress-test concern about metallicity is legitimate and, in my reading, not addressed by the current text; the 'strongly excluded' language in the abstract is also out of step with the body's own caveats."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Dear [Colleague],\n\nThis paper gives us the first completeness-corrected occurrence rate for giant planets inside the water ice line at 20–200 Myr from a dedicated NIR RV survey: 1.9^{+2.6}_{-1.4}% for 0.3–13 M_Jup within 2.5 AU, based on 85 G/K dwarfs and one planet candidate, HS Psc b. That measurement is the real contribution, and it looks carefully done. The injection-recovery completeness, the generalized binomial treatment, and the binary exclusion are all standard but executed cleanly, and the paper is transparent about its uncertainties.\n\nThe soft spots are in the interpretation, not the measurement. The abstract says a decaying planet occurrence rate is 'strongly excluded.' That's too strong. With one detection and a 2σ HDI that still touches the field rate, they can exclude only the most severe decays (young rate >1.3× the old rate at 95%), not a mild decay. The α posterior likely has a nontrivial negative tail. The body of the paper is actually more careful; the abstract should match it.\n\nThe bigger issue is the comparison with Johnson et al. (2010). The paper asserts the EGPM sample was assembled to match the stellar parameters of the field sample, including metallicity, but no [Fe/H] data or distribution comparison is presented. Johnson et al. restricted to solar metallicity, and giant planet occurrence scales steeply with metallicity. If the young moving-group stars are systematically subsolar, part of the 1.9% vs 6.5% gap could be metallicity rather than age. This is not a flaw in the rate measurement, but it's a load-bearing missing check for the evolutionary claim. The birth-environment caveat in Section 5.3 is a special case of this.\n\nAlso worth noting: the rate rests on a single unconfirmed candidate. If HS Psc b doesn't hold up, the measurement becomes an upper limit. The paper treats it as a detection, which is defensible, but the fragility deserves a sentence.\n\nWho is this for? Exoplanet demographics and formation modelers, plus anyone designing young-star RV surveys. The paper is worth a serious referee. I'd send it to review, with a request for the metallicity comparison and a softened abstract.\n\nBest.","headline":"New demographic measurement of young giant planets inside the ice line, solid but the abstract oversells the exclusion of a decaying rate and the comparison assumes a metallicity match that isn't shown.","tokens_in":53474,"tokens_out":4516,"would_cite":true,"duration_ms":51528,"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":"Young Sun-like stars have fewer giant planets inside 2.5 AU than old stars, favoring late inward migration.","keywords":["giant planet occurrence rate","young moving groups","radial velocity survey","hot Jupiter occurrence","planet migration timescales","water ice line","survey completeness","near-infrared spectroscopy"],"falsifier":"A comparable RV survey of another set of roughly 200 young G and K dwarfs with the same per-star completeness that detects eight or more giant planets inside 2.5 AU would put the young rate near the field value and refute this paper's central claim. Repeating the measurement with a young sample and a field sample matched in metallicity and birth environment would separate the age effect from the environment effect directly.","tokens_in":52514,"feed_emoji":"🪐","tokens_out":9474,"duration_ms":105440,"temperature":0.7,"pith_summary":"This paper asks when giant planets arrive close to their stars, inside the water ice line at roughly 2.5 AU, by counting such planets around 85 young (20–200 Myr) G and K dwarfs. The survey used four years of near-infrared radial velocities, and the authors tested their detection efficiency by injecting and recovering artificial planet signals. They report a completeness-corrected occurrence rate of $1.9^{+2.6}_{-1.4}\\%$ for planets with $0.3 < m \\sin i < 13\\,M_\\mathrm{Jup}$ within 2.5 AU, based on one detection, the young hot Jupiter candidate HS Psc b. This sits below the field-age rate of $6.5\\pm0.7\\%$, which the authors read as evidence that the close-in giant planet population is still being built up over Gyr timescales, although a constant rate cannot be ruled out. A decaying occurrence rate is strongly excluded by the same data.","feed_headline":"Giant planets are rare around young Sun-like stars","feed_subtitle":"A 4-year near-infrared survey finds 1.9% inside 2.5 AU at 20–200 Myr, versus 6.5% at field age.","key_machinery":"The statistical engine is a per-star search completeness map $C(P,K)$, built by fitting circular Keplerian orbits to the RVs at 100 logarithmically spaced periods and converting velocity semi-amplitude to minimum mass with stellar masses from evolutionary models. Averaging this map over the chosen period and $K$ domain yields an effective number of trials, and the occurrence rate is drawn from a generalized binomial distribution in which factorials are replaced by Gamma functions. A second component is the candidate-validation pipeline, which uses GLS periodogram significance, TESS-measured rotation periods, and correlations between RVs and activity indicators to decide which periodic signals are planets rather than stellar spots. The comparison target is a field-age survey with the same $K>20\\,\\mathrm{m\\,s^{-1}}$ and 2.5 AU boundary, making the two rates directly comparable.","core_discovery":"The central claim is that giant planets inside the water ice line are rarer at 20–200 Myr than at field age, so inward migration is still populating this region long after the protoplanetary disk has dispersed. Averaging the survey completeness over the domain $20<K<1500\\,\\mathrm{m\\,s^{-1}}$ and $P<1461\\,\\mathrm{d}$ gives an effective sample of 56 stars and one detection, from which the authors infer $f_\\mathrm{GP} = 1.9^{+2.6}_{-1.4}\\%$. A power-law model anchored to the field-age value $6.5\\pm0.7\\%$ yields a positive slope $\\alpha=0.23^{+0.14}_{-0.26}$, and the data exclude a young rate 1.3 times the field rate at 95% confidence and 1.9 times at 99% confidence. The same machinery gives a young hot Jupiter rate of $1.5^{+2.2}_{-1.1}\\%$ and a 95% upper limit of $<3.6\\%$ for brown dwarfs. The authors conclude that the close-in giant planet population is a mixture of planets formed in place or migrated early, plus planets scattered inward over $10^{8}$–$10^{9}$ yr.","pith_inferences":["If the age interpretation is right, direct-imaging surveys of nearby young stars should find a reservoir of giant planets at a few AU that later feeds the close-in population; comparing the two populations would calibrate the migration efficiency.","The birth-environment caveat can be tested directly by measuring the occurrence rate inside one large young association and comparing it with field stars matched in metallicity and mass; a difference would point to environment rather than age.","Extending the same near-infrared RV approach to sub-Jupiter masses around young stars would show whether the deficit extends down the mass function, which would suggest a common migration timescale rather than a giant-planet-specific process.","A doubled sample with the same brown-dwarf sensitivity could either confirm the very low young brown dwarf rate or reveal a population whose later disappearance would itself be an evolutionary signal."],"forward_implications":["If the young rate is truly lower, most close-in giant planets around old stars must have arrived after about 200 Myr, making long-term dynamical processes like planet-planet scattering at least as important as disk migration.","The young hot Jupiter rate of about 1.5% already matches field values, so the shortest-period giants appear to be established early while the deficit appears at longer periods within 2.5 AU.","Excluding a decaying rate rules out efficient tidal engulfment or other loss of giant planets on timescales of $10^{8}$–$10^{9}$ yr.","With larger young-star samples, the same completeness-corrected analysis could either confirm the rise in giant planet frequency or show that the rate is actually constant."],"supporting_citations":[{"why":"Supplies the field-age occurrence rate of $6.5\\pm0.7\\%$ inside 2.5 AU, the baseline against which the young rate is compared.","marker":"Johnson et al. (2010)"},{"why":"Establishes the search completeness approach of averaging detection sensitivity over period and semi-amplitude bins, which the survey adapts.","marker":"Howard et al. (2010)"},{"why":"Provides the generalized binomial / effective-number-of-trials framework used to compute occurrence rates with incomplete surveys.","marker":"Bowler et al. (2015)"},{"why":"Defines the EGPM target sample, observing strategy, and NIR RV extraction procedures on which this statistical analysis builds.","marker":"Tran et al. (2021)"},{"why":"Reports the discovery and characterization of HS Psc b, the single planet candidate counted in the occurrence rate calculation.","marker":"Tran et al. (2024)"},{"why":"Supplies the generalized Lomb-Scargle periodogram method used to identify periodic RV signals in the search for planet candidates.","marker":"Zechmeister & Kürster (2009)"},{"why":"Provides the evolutionary models used to convert stellar photometry and ages into stellar masses for the completeness map.","marker":"Baraffe et al. (1998)"}],"fun_headline_variants":["Young stars host fewer close-in giants","Giant planets rare inside young ice lines","Youth discounts giant planets near stars","Late migration shapes inner planet census","Close-in giants increase with star age"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The comparison assumes the only systematic difference between the young moving-group stars and the older field stars is age; if their birth environments differ, the inferred rise in giant planet frequency could be environmental rather than temporal.","fun_headline_variants_meta":{"raw":{"variants":["Young stars host fewer close-in giants","Giant planets rare inside young ice lines","Youth discounts giant planets near stars","Late migration shapes inner planet census","Close-in giants increase with star age"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000561,"raw_usage":{"total_tokens":2782,"prompt_tokens":1177,"completion_tokens":1605,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":793,"completion_tokens_details":{"reasoning_tokens":1545}},"tokens_in":793,"tokens_out":1605,"duration_ms":16150,"temperature":1.0,"reasoning_tokens":1545,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-07T05:20:18.923931+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A comparable RV survey of another set of roughly 200 young G and K dwarfs with the same per-star completeness that detects eight or more giant planets inside 2.5 AU would put the young rate near the field value and refute this paper's central claim. Repeating the measurement with a young sample and a field sample matched in metallicity and birth environment would separate the age effect from the environment effect directly.","supporting_citations":[],"review_version":1}