{"id":"40e64626-b4b6-454c-b56f-625e08bcac94","arxiv_id":"2411.13363","paper_version":2,"verdict":"ACCEPT","confidence":"HIGH","novelty_score":8.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"No small (1-8 Earth radii) planets with orbits under 10 days were found around 20,257 A-type stars, yielding 3-sigma upper limits below occurrence rates for Sun-like stars.","lead":"Using five years of TESS data, this study searched 20,257 bright A-type stars for small, close-in planets and found none. The resulting upper limits suggest that planets between 2 and 8 times Earth's radius become rarer around hotter, more massive stars than around Sun-like stars.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Gravity-darkening bias in the injection/recovery is plausible but quantitative; the central upper limits likely survive by a wide margin, so the ACCEPT verdict should stand pending a targeted injection test.","rationale":"I read the paper's central claim as the derived upper limits showing that small close-in planets are uncommon around A-type stars. The reader's identified weakest assumption, the representativeness of the injection model, is also the most plausible source of unquantified bias, and the paper itself flags gravity darkening in Section 3.4. However, the quantitative headroom is large: even a factor of 2-3 overestimate of sub-Neptune completeness leaves the upper limit well below G- and K-type rates, and the sub-Saturn comparison requires a much larger error to lose significance. The injection/recovery is otherwise strong: it uses real QLP light curves (capturing dilution, pulsations, and noise), a large simulated sample, and the code is released. The concern lands as a quantitative uncertainty worth testing, not as a demonstrated flaw that changes the verdict.","tokens_in":51166,"tokens_out":20414,"duration_ms":243021,"concrete_test":"Repeat the injection/recovery on roughly 2000 randomly drawn sample stars using gravity-darkened oblate-star transit models (e.g., Ahlers et al. 2020 routines) with v sin i drawn from the Zorec & Royer (2012) A-star distribution and random spin-orbit angles, using the same T0/P/b draws. Recompute the 4-8, 2-4, and 1-2 Rearth integrated completeness and the resulting 3-sigma upper limits. If the completeness changes by less than about 25%, the current conclusions are unchanged; if it falls by a factor greater than 2, Equations 9-15 should be re-evaluated and the quantitative FGK comparison softened.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The load-bearing assumption in Section 4 is that the injected transit model (circular orbit, solar-metallicity limb darkening, b drawn from [0,0.9], spherical star) represents real transits around A stars. For rapidly rotating A stars, gravity darkening makes the photospheric brightness non-uniform, so a real transit crossing the dark equator is shallower and one crossing the bright pole is deeper than the injected model; on average the detectability may shift downward, which would bias Eq. 8's completeness upward and Equations 9-15's upper limits downward. Section 3.4 acknowledges this and argues the effect is minor because typical A-star v sin i is 100-150 km/s and measured oblateness is below 0.1. This argument is plausible but not quantified in the recovery statistics. The concern is not fatal to the headline: the sub-Neptune upper limit of 9.1 per 1000 is already roughly 8x below the G-type rate, so even a factor of 2-3 completeness overestimate would leave the central conclusion intact; the sub-Saturn limit requires a greater than 4x error to lose the 3-sigma exclusion against G stars. It therefore does not overturn ACCEPT, but it is the weakest unquantified spot.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper presents the first occurrence-rate analysis of small (1–8 R_Earth), close-in (P_orb < 10 d) planets around A-type stars, using TESS full-frame-image light curves for 20,257 bright A-type stars. A custom BLS-based pipeline with automated and manual vetting yields no reliable planet candidates, and the authors characterize completeness with roughly one million injection/recovery tests that include the geometric transit probability. From the null detection they derive 3-sigma upper limits of 2.2 ± 0.4 sub-Saturns, 9.1 ± 1.8 sub-Neptunes, and 186 ± 34 super-Earths per 1000 A-type stars, and compare these with Kepler-based occurrence rates for FGKM stars. The paper discusses physical mechanisms (disk truncation, dust sublimation, photoevaporation, companions, stellar age) that could explain the inferred dearth and concludes that the occurrence rate of small close-in planets likely declines toward hotter stars, with the sub-Neptune-to-hot-Jupiter ratio possibly decreasing.","tokens_in":51351,"tokens_out":11722,"duration_ms":119262,"significance":"If the result stands, this is an important step in exoplanet demographics, extending occurrence-rate measurements from FGKM stars to the previously unconstrained regime of A-type hosts. The strength of the paper is its unusually thorough injection/recovery setup, which injects into raw light curves and passes the signals through the same flattening, detection, and vetting stages used in the real search; the thresholds are mostly fixed a priori or taken from the literature, and the code is made public. The multi-stage vetting (SPOC comparison, secondary-eclipse search, centroid offsets, ExoFOP cross-matching, TRICERATOPS) is appropriately conservative. The upper limits are robust enough to exclude Sun-like occurrence rates for sub-Saturns and sub-Neptunes at high confidence, and the comparison to existing hot-Jupiter rates gives a physically interesting suggestion about the radius cliff. The super-Earth constraint is weak, as the authors clearly acknowledge.","major_comments":[{"comment":"The completeness map is the load-bearing input for all occurrence-rate upper limits, but the injection/recovery tests assume spherical, uniformly bright stars with solar-metallicity limb darkening and impact parameters drawn from [0, 0.9]. Section 3.4 acknowledges that gravity darkening in rapidly rotating A-type stars can alter transit depth, shape, and duration, and argues qualitatively that the effect is minor for typical A-type stars. This argument is plausible but not quantified: if real transits are on average shallower or more distorted than the injected models, the true completeness would be lower than the measured 13.1%/3.2%/0.2% values, and the upper limits in Eq. (15) would be underestimated. I request either a targeted injection/recovery test using gravity-darkened transit models (e.g., following Barnes 2009 or Ahlers et al. 2020) for a representative subset of the sample, or a quantitative estimate of the maximum plausible completeness bias based on the sample's v sin i and oblateness distribution. The qualitative conclusion likely survives such a test, but the specific numbers in Section 6.1 should be placed on firmer footing.","section":"Section 4, Eqs. (8) and (15)"}],"minor_comments":[{"comment":"The caption labels the three panels as 'G-type (left), F-type (center), and A-type (left)', but the A-type panel is on the right; this is a typo that should be corrected.","section":"Figure 11 caption"},{"comment":"The completeness values for the three radius regimes are reported as 13.2% ± 2.6%, 3.1% ± 0.6%, and 0.14% ± 0.03% in the text, while the Figure 9 caption states 13.1%, 3.2%, and 0.2%. These numbers should be reconciled.","section":"Section 4 and Figure 9"},{"comment":"The phrase 'The lower T requirement removes very bright stars' is confusing because a lower T magnitude corresponds to a brighter star; the intended meaning becomes clear later, but the wording should be clarified (e.g., 'the T > 6 requirement removes saturated very bright stars').","section":"Section 2"},{"comment":"The title and abstract use the definite phrase 'Small and Close-In Planets are Uncommon around A-type Stars', while the results are upper limits and the abstract itself repeatedly says 'may be'. Consider softening the title and the first abstract sentence to '...appear to be uncommon' or '...are not found in this sample', which better matches the statistical content.","section":"Title and Abstract"}],"recommendation":"major_revision","confidential_remarks":"This is a well-executed paper that makes a valuable demographic measurement, and I think the central qualitative conclusion is very likely correct. My only substantive concern is the unquantified effect of gravity darkening on the completeness map, which directly controls all reported upper limits. A targeted injection test or a bounding calculation would resolve this; if the authors add such an analysis and it confirms their expectation, I would be happy to accept the revised version. The title is slightly stronger than the current statistical evidence supports, but that is a minor presentational point."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"This is the first occurrence-rate calculation for small (1–8 R_Earth), close-in (P<10 d) planets around A-type stars, and it's a good one. The authors search 20,257 bright TESS A-type stars, find no reliable planets, and turn that into 3-sigma upper limits: 2.2 sub-Saturns and 9.1 sub-Neptunes per 1000 stars, both well below Kepler-era rates for GK stars. The super-Earth limit (186 per 1000) is weak, and they say so. That central result—that small close-in planets are uncommon around A-type stars—holds up.\n\nWhat's new: not just the first measurement in this stellar-mass regime, but also the hint that the sub-Neptune-to-hot-Jupiter ratio drops with Teff, i.e., the radius cliff may flatten around A stars. The analysis is careful: multi-stage vetting with SPOC comparison, secondary-eclipse and centroid tests, and TRICERATOPS for the final four candidates; injection/recovery with about a million injections into raw light curves; code and data released. The derivation is non-circular: no fitted parameters force the upper limits, and the comparisons use external Kepler-based rates.\n\nThe soft spot is the one they flag themselves in Section 3.4: gravity darkening is not modeled in the injection/recovery. For a real, rapidly rotating A star, a transit crossing the dark equator is shallower than the injected spherical-star model, so true completeness could be lower than measured, which would bias the upper limits downward. The authors argue the effect is minor for typical v sin i ≈ 100–150 km/s and oblateness <0.1, and that's plausible, but it's not quantified. It's the weakest unquantified step in the paper. The good news is the central conclusion survives large errors: the sub-Neptune limit sits roughly 8x below the G-star rate, so even a factor-of-3 completeness overestimate leaves the 3-sigma exclusion intact; the sub-Saturn limit would need a >4x error to lose the G-star comparison. This is a minor-to-moderate caveat, not a fatal flaw.\n\nOther concerns are smaller. Flux dilution from unresolved companions is acknowledged and not corrected, but it matters most for the already-weak super-Earth bin. The cross-pipeline comparison to Kepler rates is inherent to the problem and handled with appropriate hedging. The authors also clearly list the missed TOIs and explain why each failed their pipeline—honest.\n\nWho's this for: anyone working on exoplanet demographics or formation/migration theory. I'd cite it and bring it to reading group.\n\nRecommendation: send it to peer review. Ask for a targeted injection/recovery run with gravity-darkened transit models (even a simple equatorial-darkening prescription) to bound that systematic, and for a short statement of how much the limits would shift. With that, it's a strong AJ paper.","headline":"First real constraint on small close-in planets around A-type stars; the null result and upper limits are solid enough to change the demographics picture, pending a targeted gravity-darkening injection test.","tokens_in":51970,"tokens_out":2431,"would_cite":true,"duration_ms":26952,"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":"A search of 20,257 A-type stars with TESS finds no reliable small planets with orbital periods under 10 days, placing 3-sigma upper limits far below those around cooler stars.","keywords":["A-type stars","exoplanet occurrence rates","TESS survey","transit detection pipeline","sub-Neptunes","hot Jupiters","injection/recovery completeness","radius cliff"],"falsifier":"Re-run the injection/recovery tests with gravity-darkened oblate-star transit models, using the measured rotation-rate distribution of A-type stars and a range of sky-projected spin-orbit angles, and measure the recovered fraction. If the completeness for sub-Neptunes falls below roughly 1%, the $3\\sigma$ upper limit rises above 30 per 1000 stars and the claimed deficit relative to G-type stars disappears; detecting a population of small close-in planets around A-type stars with future surveys at rates comparable to FGK stars would also contradict the claim.","tokens_in":50897,"feed_emoji":"🪐","tokens_out":5564,"duration_ms":53304,"temperature":0.7,"pith_summary":"This paper tries to establish the first occurrence-rate measurement of small ($1\\,R_\\oplus < R_{\\rm p} < 8\\,R_\\oplus$), close-in ($P_{\\rm orb} < 10$ days) planets around A-type stars, a population that Kepler could not constrain. Using TESS data for 20,257 bright A-type stars and a custom transit-detection and vetting pipeline, the authors find no reliable planets in this size and period range. Through injection/recovery tests they measure the pipeline completeness and convert the null detection into $3\\sigma$ upper limits: $2.2 \\pm 0.4$ sub-Saturns, $9.1 \\pm 1.8$ sub-Neptunes, and $186 \\pm 34$ super-Earths per 1000 A-type stars. These limits are more than 3 times and 6 times lower than Kepler-era estimates for sub-Saturns and sub-Neptunes around Sun-like stars, suggesting small close-in planets become rare around hot stars. The paper also argues that the ratio of sub-Neptunes to hot Jupiters drops with stellar temperature, meaning the 'radius cliff' may flatten around early-type hosts.","feed_headline":"No small close-in planets found around 20,000 A-type stars","feed_subtitle":"TESS survey sets upper limits 3–6× below Sun-like star rates, hinting hot stars destroy or block small planets.","key_machinery":"The load-bearing tool is a custom TESS transit pipeline whose completeness is calibrated by injection/recovery. The authors inject roughly 1,000,000 artificial transits into the raw light curves of the target stars, run the full detection and vetting chain, and grid the recovered fraction $R_{i,j}$ in planet-radius versus orbital-period cells; weighting by the geometric transit probability $p_{\\rm geo,k}\\approx R_{\\star,k}/a_k$ yields the completeness map $C_{i,j}$. The occurrence-rate upper limit then follows from the binomial formula $f_{\\rm cell,upper}=1-(1-CI)^{1/(n_{\\rm trial}+1)}$ with $n_{\\rm trial}=n_\\star C$, applied separately to sub-Saturns ($4-8\\,R_\\oplus$), sub-Neptunes ($2-4\\,R_\\oplus$), and super-Earths ($1-2\\,R_\\oplus$). The overall measured completeness is only 7.2%, which explains why the null detection translates into a weak super-Earth limit but a relatively strong sub-Neptune limit.","core_discovery":"The central discovery is a null result with quantitative force: no bona fide transiting planets with radii $1-8\\,R_\\oplus$ and periods $0.5-10$ days orbit the 20,257 A-type stars searched, and the completeness-corrected binomial upper limits place the occurrence rates of sub-Saturns, sub-Neptunes, and super-Earths at $<2.2$, $<9.1$, and $<186$ per 1000 stars at $3\\sigma$. The sub-Saturn and sub-Neptune limits are over 3 and 6 times lower than the corresponding Kepler-derived rates for G-type stars, and the super-Earth limit is more than 1.5 times lower than for M dwarfs. The paper interprets this as evidence that small close-in planets cannot easily form at, migrate to, or survive at short orbital periods around A-type stars, and it notes the occurrence rate of sub-Neptunes appears to decline with stellar temperature faster than that of hot Jupiters, flattening the radius cliff.","pith_inferences":["If the deficit is real, the same mechanism should suppress planets at somewhat longer periods around A-type stars; the authors' dust-sublimation argument predicts a gradual onset rather than a sharp cutoff at 10 days, which future TESS cycles or PLATO could test by pushing to roughly 20-30 days.","The upper-limit methodology could be sharpened by injecting gravity-darkened transit models directly into the recovery tests; a factor-of-two change in completeness for the $4-8\\,R_\\oplus$ bin would shift the sub-Saturn limit to within a factor of about 2 of the G-star rate, so the claimed deficit is testable with modest modeling effort.","Applying the same pipeline to F-type stars would separate the stellar-temperature trend from survey-specific detection losses, since the A-type deficit is currently established against Kepler pipelines with different completeness functions.","The super-Earth upper limit of 186 per 1000 stars is too weak to constrain formation physics; detecting super-Earth cores around A-type stars would likely require combining TESS with radial-velocity or transit-timing follow-up, or waiting for a larger sample from extended TESS sectors."],"forward_implications":["Small close-in planets are rarer around A-type stars than around G-type stars by factors of at least 3 (sub-Saturns) and 6 (sub-Neptunes), if the upper limits reflect the true rates.","The dearth of sub-Neptunes compared with hot Jupiters around A-type stars (ratio $< 3.1 \\pm 0.8$, versus $12.9 \\pm 3.9$ for G-type stars) suggests the radius cliff flattens with increasing host-star temperature.","Planets that do exist around A-type stars may be stripped to bare rocky cores by near-ultraviolet photoevaporation, leaving super-Earths that current TESS data cannot detect.","White dwarf pollution is unlikely to come from close-in planets that survive the main-sequence phase; the scarcity of small close-in planets around A-type stars supports a wide-separation origin for white dwarf contaminants.","The absence of sub-Saturn and sub-Neptune detections at $P<10$ days is consistent with formation and migration being inhibited interior to the dust sublimation radius (roughly $0.12$ AU around a typical A star)."],"supporting_citations":[{"why":"Supplies the M-dwarf sub-Saturn occurrence rate used as the low-temperature comparison point.","marker":"Dressing & Charbonneau 2013"},{"why":"Supplies M-dwarf sub-Neptune and super-Earth occurrence rates in the same radius bins used for comparison.","marker":"Dressing & Charbonneau 2015"},{"why":"Provides the FGK-star occurrence rates for sub-Saturns, sub-Neptunes, and super-Earths that the A-type upper limits are compared against.","marker":"Kunimoto & Matthews 2020"},{"why":"Provides hot Jupiter occurrence rates around G-, F-, and A-type stars that anchor the radius-cliff flattening comparison.","marker":"Beleznay & Kunimoto 2022"},{"why":"Supplies the box least-squares algorithm that is the core period-search step of the detection pipeline.","marker":"Kovacs et al. 2002"},{"why":"Supplies the quadratic limb-darkening coefficients used both to inject artificial transits and to model detected signals.","marker":"Claret 2017"}],"fun_headline_variants":["No small close-in planets found around 20,257 A-type stars","TESS finds no 1–8 Earth-radius planets near A-type stars","A-type stars lack close-in small planets in TESS data","Upper limits: small planets scarce around A-type stars","No transiting small planets found around 20k A-type stars"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The upper limits assume that the artificial transits used in injection/recovery tests—circular orbits, solar-metallicity limb darkening, and impact parameters drawn from $[0,0.9]$—look like real transits around A-type stars; if rapid rotation, gravity darkening, or other unmodeled effects make real transits shallower or more distorted, the true completeness is lower than 7.2% and the upper limits are biased downward.","fun_headline_variants_meta":{"raw":{"variants":["No small close-in planets found around 20,257 A-type stars","TESS finds no 1–8 Earth-radius planets near A-type stars","A-type stars lack close-in small planets in TESS data","Upper limits: small planets scarce around A-type stars","No transiting small planets found around 20k A-type stars"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000728,"raw_usage":{"total_tokens":3364,"prompt_tokens":1151,"completion_tokens":2213,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":767,"completion_tokens_details":{"reasoning_tokens":2123}},"tokens_in":767,"tokens_out":2213,"duration_ms":19061,"temperature":1.0,"reasoning_tokens":2123,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-12T16:30:11.205030+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Re-run the injection/recovery tests with gravity-darkened oblate-star transit models, using the measured rotation-rate distribution of A-type stars and a range of sky-projected spin-orbit angles, and measure the recovered fraction. If the completeness for sub-Neptunes falls below roughly 1%, the $3\\sigma$ upper limit rises above 30 per 1000 stars and the claimed deficit relative to G-type stars disappears; detecting a population of small close-in planets around A-type stars with future surveys at rates comparable to FGK stars would also contradict the claim.","supporting_citations":[],"review_version":1}