{"id":"4c317042-5a4c-416a-ab9c-8c02bd77fd69","arxiv_id":"2505.22030","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"A new grid of core-collapse supernova yields for 9.22-15 solar mass stars shows that the lowest-mass exploding stars contribute negligibly to averaged galactic chemical enrichment.","lead":"This paper computes the chemical elements produced by medium-sized stars (9 to 15 times the Sun's mass) when they explode as supernovae. It shows that these stars contribute almost nothing to the average chemical makeup of a generation of stars, but they matter for understanding individual supernova observations.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The 'negligible' claim rests on a factor-of-2 threshold, which for flat-yield isotopes (e.g., 13C, 15N) permits non-negligible 9-13 Msun contributions of ~20-40%.","rationale":"The reader identified black-hole formation as the weakest assumption, but that concern does not threaten the paper's main quantitative conclusion: if low-mass stars collapse to black holes, their ejected yields are zero, making the 9-13 Msun contribution even smaller and the 'negligible' claim stronger. The actual load-bearing weakness is the metric used to define 'negligible'. The paper's own statement—'negligible ... at least within a factor of ~2'—implies that the IMF-averaged yields with and without the 9-13 Msun range agree to within a factor of 2. That is a very permissive threshold: a 50% contribution from 9-13 Msun would satisfy it. Table 2 shows that a subset of isotopes (13C, 15N, 17O, 19F, and some others) have yields that are only weakly dependent on initial mass, so their IMF-weighted contribution is expected to be substantial. Without seeing the actual ratios in Figure 11, the abstract's 'negligible for essentially all isotopes' goes beyond what is demonstrated. We therefore recommend keeping the conditional verdict, with the condition being a re-analysis or a softened claim, rather than the black-hole caveat.","tokens_in":533,"tokens_out":11134,"duration_ms":326261,"concrete_test":"Compute, for every isotope in Table 2, the IMF-weighted yields <Y>_{9.22-120} and <Y>_{13-120} using a Salpeter IMF (dN/dM ∝ M^{-2.35}) and the yields from Limongi & Chieffi (2018) for M>15 Msun, following the same integration method as the paper. For each isotope calculate the 9-13 Msun fractional contribution f = 1 - <Y>_{13-120}/<Y>_{9.22-120}. If any isotope with near-flat yields (e.g., 13C, 15N, 17O, 19F) has f > 0.2, the 'negligible' claim is not supported by the factor-of-2 criterion and the abstract should be revised to identify the exceptions.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim that 9.22-13 Msun stars contribute negligibly to IMF-averaged yields is based on Figure 11, where 'negligible' is operationalized as <Yield>_{9.22-120} and <Yield>_{13-120} agreeing within a factor of ~2. This criterion is too loose: a factor of 2 concordance can mean that the 9-13 Msun contribution equals 100% of the >13 Msun contribution (i.e., 50% of the total), which is not negligible. Moreover, Table 2 shows that several isotopes, notably 13C, 15N, 17O, and 19F, have yields that are nearly independent of initial mass (e.g., 13C yield varies only from 4.4e-4 to 7.3e-4 across 9.22-15 Msun). For a Salpeter IMF, about 38% of stars with M>9.22 Msun lie in 9.22-13 Msun; if yields are flat, these stars contribute ~38% of the total IMF-averaged yield from 9.22-120 Msun, and the ratio <Yield>_{9-120}/<Yield>_{13-120} is ~1.62, still within a factor of 2. Thus the abstract's phrase 'negligible for essentially all the isotopes' overstates what the presented test supports. The reader's black-hole-formation concern is less load-bearing for the averaged-enrichment claim: if some of these stars fail to explode, their yields vanish, which would only reduce the 9-13 contribution and strengthen the 'negligible' conclusion, though it would affect the individual yields and light-curve predictions. The decisive issue is the operational definition of 'negligible'.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper computes hydrostatic and explosive nucleosynthesis for non-rotating, solar-metallicity stars with initial masses 9.22, 10, 11, 12, 13, and 15 Msun, using the FRANEC stellar evolution code with a 335-isotope network and the HYPERION thermal-bomb explosion code. The mass cut is calibrated by the external initial-mass--ejected-56Ni relation of Burrows et al. (2024), and the same relation together with the Burrows et al. explosion-energy relation is used to compute bolometric light curves. The main results are: (1) alpha-element yields decrease steeply with decreasing mass below about 15 Msun; (2) weak-s yields decrease almost linearly in a log sense; and (3) IMF-averaged yields over 9.22-120 Msun and over 13-120 Msun agree within a factor of about 2, which the authors interpret as a negligible contribution from 9.22-13 Msun stars. The paper also compares isotopic ejecta to solar composition and discusses differences from the earlier Limongi & Chieffi (2018) yields caused by the inhibition of breathing pulses.","tokens_in":29059,"tokens_out":6971,"duration_ms":70240,"significance":"If the models are correct, this yield grid fills an important mass range for galactic chemical evolution studies, and the light-curve predictions provide a useful interpretive tool for low-mass core-collapse supernovae. The paper has clear strengths: the codes and input physics are documented, the 56Ni-mass cut is tied to an external 3D simulation result rather than fitted to the paper's own yields, detailed isotopic yield tables are provided, and the authors are transparent about the breathing-pulse treatment and about differences from earlier calculations. However, the central claim that 9.22-13 Msun stars contribute negligibly to IMF-averaged yields is not supported by the factor-of-2 test as stated, because several isotopes have nearly mass-independent yields. With a revised, quantitative definition of 'negligible' and an explicit per-isotope accounting, the paper would be a solid and useful contribution.","major_comments":[{"comment":"The central claim stated in the abstract and in Section 4, that the 9.22-13 Msun contribution to IMF-averaged yields is negligible for essentially all isotopes, is not established by the test used in Figure 11. The text defines 'negligible' as agreement between <Yield>_{9.22-120} and <Yield>_{13-120} within a factor of about 2, but for an isotope whose yield is independent of initial mass, a Salpeter IMF places about 38% of the stars in the 9.22-13 Msun bin, so that bin contributes about 38% of the total 9.22-120 Msun yield and the ratio <Yield>_{9.22-120}/<Yield>_{13-120} is about 1.6, which passes the stated criterion. Table 2 shows that this flat-yield situation is realized for several isotopes: 13C varies only from 4.37e-4 to 7.29e-4 Msun, 17O from 5.41e-5 to 5.73e-5, 15N from 5.28e-6 to 7.38e-6, and 19F from 3.22e-6 to 4.19e-6 across the 9.22-15 Msun grid. For these isotopes the 9.22-13 Msun contribution is therefore not negligible, and the phrase 'essentially all the isotopes' overstates what the test supports. Please replace the factor-of-2 comparison with explicit fractional contributions per isotope, or qualify the claim accordingly.","section":"Section 4, Figure 11, and Table 2"},{"comment":"The paper assumes in Section 1 that all stars with M >= 9.22 Msun 'eventually explode as core collapse supernovae' and uses that assumption for every yield calculation and for the light curves in Section 5. The possibility that some of these progenitors, particularly in the 9-11 Msun range, might instead collapse to black holes is not discussed in the context of the yields. If any of these models fail to explode, their yields vanish and their predicted light curves do not apply; the IMF-averaged 'negligible contribution' claim would be strengthened, but the individual yields and the statement that these models can interpret specific supernovae would need to be conditional. The manuscript should either justify the explosion assumption for these structures (for example with compactness or explodability criteria) or explicitly state that the yields and light curves are upper limits or conditional predictions under the assumed explosion, and discuss how that affects the abstract's claims.","section":"Section 1 and Section 5"},{"comment":"The inhibition of breathing pulses is justified by the Constantino et al. (2016) analysis of low-mass stars in globular clusters, but the models here are intermediate-mass stars of 9-15 Msun, and the paper does not discuss whether that conclusion transfers to this mass range. This choice changes the 12C abundance in the He-exhausted core and produces non-negligible differences in the C-burning products Ne, Mg, and Al relative to Limongi & Chieffi (2018), as the authors note. Because these elements are part of the yield grid, the systematic uncertainty introduced by the extrapolation should be quantified or at least discussed more explicitly, rather than presented as a settled modeling decision.","section":"Section 4, last paragraph"}],"minor_comments":[{"comment":"The heading reads 'NUCLEAR NUCLEAR NETWORK'; the duplicated word should be removed.","section":"Section 2 heading"},{"comment":"There are several typographical errors, including 'inital' in the abstract, 'to to' in the abstract and Section 2, and 'calcutions' in the Table 3 caption.","section":"Abstract and text"},{"comment":"The numbered conclusions skip from item (10) to item (12); an item (11) appears to be missing or misnumbered.","section":"Section 6"},{"comment":"The statement that observed element abundance ratios in a core-collapse supernova spectrum can be used to infer a low-mass progenitor is illustrated only schematically; adding a concrete example with a specific observed supernova would make the claim more useful and testable.","section":"Figure 6"},{"comment":"The light-curve predictions depend on the assumed 56Ni mixing extent and the explosion-energy relation, and the paper notes this dependence; please state explicitly in the text that the plateau luminosities and durations in Figure 12 are not robust predictions but rather examples tied to these choices, which is already implied but would be clearer as an explicit caveat.","section":"Section 5"}],"recommendation":"major_revision","confidential_remarks":"The manuscript is within the scope of the journal and the model grid is useful. The main concern is the overstated 'negligible' claim, which the authors should be able to fix by quantifying per-isotope fractional contributions and by softening or revising the abstract accordingly. The explosion assumption and the breathing-pulse extrapolation should also be discussed as limitations. I found no indication of problems with citation practices or data provenance."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"The useful thing here is a new grid of CCSN yields for 9.22, 10, 11, 12 Msun, computed with the same FRANEC/HYPERION setup as Limongi & Chieffi 2018. That fills a real gap. The authors are also careful to calibrate the 56Ni mass cut to Burrows et al. 2024 rather than fitting their own yields, and they give the whole isotope table in the text. Credit where due: this is a solid, citable model grid.\n\nMy main reservation is the headline claim that the 9.22-13 Msun contribution is 'negligible for essentially all isotopes.' The operational test is Figure 11: agreement within a factor of 2 between <Yield>_{9.22-120} and <Yield>_{13-120}. That is a loose bar. For isotopes with nearly mass-flat yields (13C, 15N, 17O, 19F in Table 2), the 9-13 Msun stars carry ~38% of the IMF-integrated yield (a Salpeter count argument). The ratio 1.62 is within a factor of 2, yet the low-mass contribution is not negligible in any ordinary sense. The abstract overstates what the figure supports.\n\nI do not think this sinks the paper. The yields themselves are the deliverable, and the steep decline for alpha elements is clear. But the abstract and Section 4 should be recalibrated: either define 'negligible' quantitatively per isotope, or soften the claim to 'within a factor of 2' rather than 'negligible.' A second, minor point: the paper assumes all six models explode; if some low-mass ones fail, the averaged contribution shrinks further, so it does not affect the central enrichment argument, but it should be acknowledged given the ongoing debate about the lowest CCSN mass. Also, the codes are not public and no independent yield comparison is shown – typical for this group, but it makes the grid hard to validate.\n\nRecommendation: send to peer review. It is a standard but useful grid paper with a headline that needs tempering. A good referee will ask for the factor-of-2 issue to be addressed. I would not desk-reject.","headline":"Valuable new low-mass CCSN yields, but the 'negligible' IMF claim is softer than the abstract implies because the factor-of-2 criterion still allows ~40% contributions from the 9-13 Msun bin for flat-yield isotopes.","tokens_in":29677,"tokens_out":3805,"would_cite":true,"duration_ms":32817,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"Stars from roughly 9 to 13 solar masses contribute negligibly to the average chemical enrichment of a generation of massive stars, even though their yields decline steeply with mass and their individual models remain essential for…","keywords":["core-collapse supernova yields","stellar nucleosynthesis","low-mass massive stars","Salpeter IMF averaging","weak s-process","HYPERION thermal-bomb explosions","galactic chemical evolution","supernova light curves"],"falsifier":"A secure observation of a roughly 9 to 11 solar-mass supernova progenitor whose ejected material contains as much oxygen, neon, or magnesium as a 15 solar-mass model would contradict the claimed steep decline in yields with decreasing mass. Alternatively, if realistic explosion simulations showed that 9.22 to 12 solar-mass stars fail to explode, the averaged yields of this mass range would drop to zero, and the negligible-contribution conclusion would need to be replaced by a black-hole formation budget.","tokens_in":28475,"feed_emoji":"💫","tokens_out":13866,"duration_ms":107929,"temperature":0.7,"pith_summary":"This paper computes the full chemical yields of solar-metallicity, non-rotating stars of 9.22, 10, 11, 12, 13, and 15 solar masses, the lowest-mass stars that are assumed to explode as core-collapse supernovae, and asks what they contribute to the enrichment of a stellar generation. The central result is that when yields are averaged over a standard Salpeter initial mass function, the stars from 9.22 to 13 solar masses contribute negligibly to essentially every isotope, within the factor of about two that the authors adopt as their numerical uncertainty. The yields of intermediate-mass elements, oxygen through phosphorus, fall steeply as the initial mass decreases, and the weak-s-process elements from gallium to zirconium decline almost linearly in logarithm with mass. If these models are right, galactic chemical evolution codes can ignore this mass range when computing average enrichment, while the individual models remain essential for interpreting specific supernovae, and the paper provides bolometric light curves for that purpose.","feed_headline":"The lightest supernova stars add almost nothing to galactic chemistry","feed_subtitle":"The new models find 9-13 solar-mass stars barely change average galaxy chemistry, yet stay key for individual supernovae.","key_machinery":"The argument is carried by a grid of six presupernova models recomputed with the same stellar evolution input as the preceding study but with a 335-isotope nuclear network, coupled to explosive nucleosynthesis from the HYPERION thermal-bomb code. The explosion is induced by depositing thermal energy at the base of the ejecta, tuned to yield about $10^{51}$ erg of kinetic energy, with the mass cut, the boundary between the remnant and the ejecta, fixed by an adopted initial-mass versus ejected-$^{56}$Ni relation taken from three-dimensional supernova simulations. The decisive quantitative step is the comparison of yields averaged over a Salpeter IMF in the mass ranges 9.22-120 $M_\\odot$ and 13-120 $M_\\odot$, which is what demonstrates the negligible contribution of the low-mass end. A secondary mechanism affects the shape of the trend: the second dredge-up in the 9.22 $M_\\odot$ model shrinks the helium core and makes the presupernova density gradient nearly vertical between the 10 and 9.22 $M_\\odot$ models, which alters shock propagation and the innermost explosive yields.","core_discovery":"The paper claims that the lowest-mass core-collapse supernova progenitors are chemically negligible in bulk but individually diagnostic. Comparing the IMF-averaged ejecta of a generation of 9.22 to 120 solar-mass stars with the average over just 13 to 120 solar masses, it finds that the 9.22 to 13 solar-mass stars change the yield of essentially every isotope by less than the factor-of-two uncertainty band. It also finds that the alpha-element yields, carbon through calcium, decline by more than an order of magnitude from 15 down to 9.22 solar masses, and that the weak-s component from gallium to zirconium decreases nearly linearly with mass, with the more neutron-rich isotopes underproduced. Because of this steep decline, linearly extrapolating yields from more massive stars down to this range would substantially overestimate the true yields. The authors nevertheless emphasize that these models can be used to interpret individual supernovae, and they show that ratios of some odd-Z to even-Z elements in the ejecta may identify a low-mass progenitor.","pith_inferences":["If some 9 to 12 $M_\\odot$ progenitors actually collapse to black holes rather than exploding, the negligible-contribution result would become stronger for IMF-averaged chemistry, but the individual-supernova interpretation would lose those cases.","The near-vertical density jump between the 10 and 9.22 $M_\\odot$ models marks a sensitive boundary: modest changes in convective overshooting or mass loss could shift which stars explode, and the averaged yield budget would change at the margin.","The mass-cut prescription, adopting an ejected-$^{56}$Ni versus initial-mass relation, is a modelling choice; the authors state that the data for alternative mass cuts are available, so the robustness of the negligible-contribution conclusion could be tested directly.","Rotation, which the authors flag for future work, could enlarge stellar cores and move the mass range that dominates enrichment downward, potentially making the low-mass yields non-negligible."],"forward_implications":["Galactic chemical evolution models can omit the 9.22 to 13 $M_\\odot$ stars from IMF-averaged yields without changing the predicted isotope pattern beyond the quoted factor of about two.","Log-linear extrapolations of yields from more massive stars down to the 9 to 13 $M_\\odot$ range overestimate most element yields, so the actual model yields are needed for accurate enrichment histories.","The contrasting behaviour of even-Z and odd-Z elements, for example sodium, aluminium, and phosphorus versus nitrogen, fluorine, potassium, and scandium, gives a spectroscopic way to identify a low-mass core-collapse supernova progenitor.","The models predict plateau light curves with luminosity $\\log(L/L_\\odot)\\sim 41.5$ to $42.1$ at 30 days and plateau durations of roughly 110 to 140 days, with a non-monotonic mass dependence caused by the adopted explosion-energy relation.","The 13 and 15 $M_\\odot$ yields for neon, magnesium, and aluminium differ from earlier published values because the new models suppress convective breathing pulses and therefore retain more $^{12}$C in the helium-exhausted core."],"supporting_citations":[{"why":"It defines the evolutionary properties and final fates of 7 to 15 $M_\\odot$ stars and sets the 9.22 $M_\\odot$ core-collapse threshold used here.","marker":"Limongi et al. (2024)"},{"why":"It provides the HYPERION code and the thermal-bomb explosion method used for explosive nucleosynthesis and light-curve calculations.","marker":"Limongi & Chieffi (2020)"},{"why":"It supplies the 335-isotope nuclear network, the yields of more massive stars used in the IMF average, and the comparison yields for 13 and 15 $M_\\odot$.","marker":"Limongi & Chieffi (2018)"},{"why":"It supplies the initial-mass versus ejected-$^{56}$Ni relation used to fix the mass cut in every model.","marker":"Burrows et al. (2024)"},{"why":"It underlies the stellar evolution code version used to compute the presupernova models.","marker":"Chieffi & Limongi 2013"},{"why":"It provides the observational argument against convective breathing pulses that motivates the higher core carbon abundances in the new models.","marker":"Constantino et al. (2016)"},{"why":"It supports the claim that the steep density gradient at the lowest masses affects shock development and therefore the yields.","marker":"Boccioli et al. 2023"}],"fun_headline_variants":["Low-mass supernova progenitors barely alter galactic chemistry","9-13 solar-mass stars nearly invisible in average yields","Lightest supernova stars: negligible for galaxies, key for individuals","Steep yield drop makes lowest CCSNe progenitors negligible","Bulk yields ignore 9-13 solar-mass stars, but individual sights matter"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The paper assumes that every star in the grid, including the 9.22 and 10 solar-mass stars, actually explodes as a supernova rather than collapsing quietly into a black hole; if any of them fails to explode, its yields vanish and the averaged contribution changes.","fun_headline_variants_meta":{"raw":{"variants":["Low-mass supernova progenitors barely alter galactic chemistry","9-13 solar-mass stars nearly invisible in average yields","Lightest supernova stars: negligible for galaxies, key for individuals","Steep yield drop makes lowest CCSNe progenitors negligible","Bulk yields ignore 9-13 solar-mass stars, but individual sights matter"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.00039,"raw_usage":{"total_tokens":2104,"prompt_tokens":1049,"completion_tokens":1055,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":665,"completion_tokens_details":{"reasoning_tokens":968}},"tokens_in":665,"tokens_out":1055,"duration_ms":7239,"temperature":1.0,"reasoning_tokens":968,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-07T13:16:43.986010+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A secure observation of a roughly 9 to 11 solar-mass supernova progenitor whose ejected material contains as much oxygen, neon, or magnesium as a 15 solar-mass model would contradict the claimed steep decline in yields with decreasing mass. Alternatively, if realistic explosion simulations showed that 9.22 to 12 solar-mass stars fail to explode, the averaged yields of this mass range would drop to zero, and the negligible-contribution conclusion would need to be replaced by a black-hole formation budget.","supporting_citations":[{"cited_title":"2024, ApJS, 270, 29","cited_arxiv_id":null,"evidence_quote":"It defines the evolutionary properties and final fates of 7 to 15 $M_\\odot$ stars and sets the 9.22 $M_\\odot$ core-collapse threshold used here."},{"cited_title":"2018, ApJS, 237, 131985, ApJ, 296, 204","cited_arxiv_id":null,"evidence_quote":"It supplies the 335-isotope nuclear network, the yields of more massive stars used in the IMF average, and the comparison yields for 13 and 15 $M_\\odot$."},{"cited_title":"2024, ApJL, 964, L16","cited_arxiv_id":null,"evidence_quote":"It supplies the initial-mass versus ejected-$^{56}$Ni relation used to fix the mass cut in every model."},{"cited_title":"2013, ApJ, 764, 21","cited_arxiv_id":null,"evidence_quote":"It underlies the stellar evolution code version used to compute the presupernova models."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"It supports the claim that the steep density gradient at the lowest masses affects shock development and therefore the yields."}],"review_version":1}