The Occurrence and Impact of Carbon-Oxygen Shell Mergers in Massive Stars

A. Chieffi; A. Falla; A. Sieverding; H.E. Brinkman; L. Roberti; M. Limongi; M. Lugaro; M. Pignatari; S. K. Jeena

REVIEW

The Occurrence and Impact of Carbon-Oxygen Shell Mergers in Massive Stars

L. Roberti, M. Pignatari, H.E. Brinkman, S. K. Jeena, A. Sieverding, A. Falla, M. Limongi, A. Chieffi

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M. Lugaro

Solar and Stellar Astrophysics · Submitted 26 Apr 2025 · 25 references

Pith's verdict: A useful, transparent compilation and a plausible physical screen for C-O shell mergers, but the headline 90% recall statistic is contradicted by the paper's own box counts and the EMP claim outruns the current analysis.

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arXiv ID2504.18867 (version 1)

Pith ID4QLHSZCB, Pith's permanent record of this paper and its review

CitationA. Chieffi, A. Falla, A. Sieverding, H.E. Brinkman, L. Roberti, M. Limongi, M. Lugaro, M. Pignatari, S. K. Jeena. "The Occurrence and Impact of Carbon-Oxygen Shell Mergers in Massive Stars." arXiv:2504.18867 (2025). https://pith.science/paper/4QLHSZCB

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The paper delivers a useful and honestly limited screen for C-O shell mergers — low CO core mass and low central carbon after He burning — backed by a broad compilation of 209 published models. But the headline 90% recall statistic does not survive contact with the paper's own numbers: the box of 79 models contains 38 non-mergers, leaving 41 mergers, which equals the full merger count, so recall is 100%, not 90%. That internal inconsistency sits at the center of the paper's main quantitative claim and must be fixed.

The genuinely new piece is the MCO–XC12 diagnostic: a small He-exhausted core and a low central 12C fraction plausibly reduce the entropy barriers that keep the O-burning shell from penetrating the C-rich layers. The compilation is a real service — the appendix tables list all 209 models with codes, masses, metallicities, and rotation velocities, and the nucleosynthesis discussion of odd-Z production via light-particle captures is solid. I also credit the authors for stating plainly that the box is necessary but not sufficient and that the in-box merger likelihood is only about 50%.

The soft spots are real but mostly fixable. First, the thresholds are fitted on the same 209 models used to compute the recall and the likelihood, so the predictive claim is in-sample; the text even notes that different convective criteria or a larger 12C(α,γ)16O rate shift the boundary. Second, the 90% vs 100% discrepancy is not cosmetic — it suggests the thresholds were chosen to enclose essentially all merger models, and the reported 90% is either a mis-statement or a different statistic. Third, the stellar-archaeology argument is qualitative: the claim that a C-O merger contribution is 'essential' at extremely low metallicity rests on a quadrant decomposition of [K/Mg] vs [Sc/Mg], not on a quantitative mixture or GCE fit. The authors admit they cannot yet estimate the required merger fraction, which is the honest thing to do, but it also means the conclusion is overstated for now.

The paper is readable, the data are transparent, and the physical reasoning is clear. It deserves a serious referee; with a corrected statistic, an out-of-sample check (e.g., leave-one-set-out on the different model families), and a scaled-back wording of the EMP conclusion, it would be a solid contribution. I'd send it to review.

Referee report

Major objections (4)

[Section 2 and Abstract] The statement that '90% of models that undergo a C-O merger have XC12<0.277 and MCO<4.90 M⊙' is not reproducible from the paper's own numbers. The paper states that there are 41 merger models total and that the threshold box contains 79 models, of which 38 do not exhibit a merger; this implies that all 41 mergers are inside the box (100% recall), not 90%. If the intended recall were 90% (about 37 of 41 mergers), the box would need to contain 42 non-mergers rather than the stated 38. The abstract and Section 2 must be corrected to give a consistent set of counts, and the headline statistic should be recomputed accordingly.
[Section 2, Fig. 1] The thresholds XC12<0.277 and MCO<4.90 M⊙ are chosen by inspecting the same 209 models used for the evaluation, so the reported 90% (or 100%) recall and the 'likelihood of about 50%' are in-sample statistics, not out-of-sample predictions. As a result, the claim that this 'provides a method to predict the occurrence of these events from the first evolutionary phases' is not yet established. The authors should either perform an out-of-sample validation (for example, leave-one-out cross-validation or holding out one or more complete model sets) or explicitly reframe the result as a descriptive property of current 1D stellar models.
[Section 4, Fig. 5] The conclusion that 'a nucleosynthetic contribution from C-O shell mergers is essential even at extremely low metallicity' goes beyond what the figure shows. The observed [K/Mg] and [Sc/Mg] values scatter in a junction region among the three model populations; the authors themselves note that the PUSH models reach [Sc/Mg]≳0 without a merger; and no statistical test or quantitative mixture analysis is presented. The data are consistent with C-O mergers being one contributing channel among several, but 'essential' requires a demonstration that no combination of non-merger yields can reproduce the observed joint distribution.
[Appendix B, Table B.1 and Fig. 5] The PUSH models are a key non-merger comparison set, but the appendix states that their yields include only material reaching temperatures above 1.75 GK, which excludes about 50% of the total Mg yield. Since [K/Mg] and [Sc/Mg] normalize to Mg, an excluded half of the Mg denominator would raise the quoted ratios by roughly 0.3 dex (because the denominator is halved); the assertion that this has no significant impact needs to be justified quantitatively, or the yields should be corrected to include the full Mg production.

Minor objections (5)

[Section 2] The text says '77%, 132 out of 172' for non-merger models outside the box, but the paper counts 41 mergers out of 209, so the number of non-merger models is 168, not 172. Please correct the denominator.
[Fig. 1 caption] The grey areas are described as 'covariant confidence ellipses' centred at MCO=4.02 and XC12=0.176, but the selection thresholds discussed in the text are the straight lines XC12<0.277 and MCO<4.90. The relationship between the ellipses and the box should be clarified in the caption or the text.
[Section 6] The statement that 'the occurrence of C-O mergers does not depend on the initial mass, rotational velocity, nor metallicity' is too strong; the paper's own Section 2 states that these parameters act indirectly through MCO and XC12. A formulation such as 'depends on MCO and XC12, which in turn are affected by mass, metallicity, and rotation' would be more accurate.
[Appendix B] The phrase 'outside of this regions' should be 'outside this region'; in addition, the sentences describing the PUSH Mg-yield normalization should be rewritten for clarity, as they currently appear to conflict with the stated exclusion of half the Mg yield (see major comment 4).
[Table C.1] Consider adding explicit error bars for each star, or state clearly that a representative error bar from Roederer et al. (2014) is used because JINAbase does not provide individual uncertainties; the current text is somewhat ambiguous about this.

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The paper

The paper claims

The occurrence of C-O shell mergers in massive stars can be predicted from two quantities after helium burning.

The reading

The paper sets out to find early warning signs of carbon-oxygen shell mergers, the late-stage convective events in massive stars in which the oxygen burning shell ingests carbon and neon from the layers above it. Analysing 209 published one-dimensional stellar models spanning 9.2 to 25 solar masses and metallicities from zero to near-solar, it claims that whether a model merges is fixed already at the end of central helium burning: 90% of merging models have a CO core mass below 4.90 solar masses and a central 12C mass fraction below 0.277. It then argues that the distinctive nucleosynthesis of the merger, rich in the odd-Z elements potassium and scandium, is visible in the most metal-poor stars of the Galaxy, so a C-O merger contribution is required even at extremely low metallicity. A reader should care because this turns a rare late-stage accident into a predictable, testable property of the progenitor and ties it to the long-standing underproduction of K and Sc in massive-star nucleosynthesis.

What carries the argument

The machinery is the $M_{\rm CO}$--$X_{\rm C12}$ diagram: the CO core mass and the central $^{12}$C mass fraction at the end of central helium burning. These two numbers control both the spacing of the later burning shells and the strength of the entropy barriers between them: a smaller CO core packs the C, Ne, and O shells closer together, and a lower $^{12}$C abundance reduces the $^{20}$Ne left by carbon burning, which weakens the entropy discontinuity that normally keeps the O shell from penetrating into the C-rich layers. The paper uses the location of 209 models in this plane, with covariance ellipses centred on the average merger values, to define the grey box that contains 90% of merger models. The same physics then drives the nucleosynthetic signature: mixed-in carbon at roughly 2.6 to 2.8 $\times 10^9$ K activates $^{12}$C+$^{12}$C, $^{12}$C+$^{16}$O, and $^{16}$O+$^{16}$O fusions together with the $^{20}$Ne(γ,α) reaction, and the released protons and alphas are captured by species like $^{34}$S to build up $^{35}$Cl, $^{39}$K, and $^{45}$Sc.

Extended reading notes

Core claim

In stars of roughly 9 to 25 solar masses, the final collapse can be preceded by a C-O shell merger: the convective oxygen burning shell ingests carbon-rich material from the overlying C/Ne layers, forming one large mixed convective region. The paper's central claim is that this event is not a stochastic accident of the last days but is determined by the structure left by helium burning. Specifically, at least 90% of models that undergo a merger have a CO core mass $M_{\rm CO} < 4.90\,M_\odot$ and a central carbon abundance $X_{\rm C12} < 0.277$, with average values of $4.02\,M_\odot$ and $0.176$. The thresholds are necessary but not sufficient, since models inside the box merge with only about 50% likelihood. The paper further claims that the merger's yields, especially the odd-Z elements $^{39}$K and $^{45}$Sc, are primary and independent of metallicity, and that comparing merger and non-merger yields with abundances in extremely metal-poor stars shows that a contribution from C-O mergers is essential even at $[\rm Fe/H] < -3$.

Load-bearing premise

The predictive box is trustworthy only if the 209 heterogeneous one-dimensional models, with their different convection criteria and reaction rates, sample the real conditions under which C-O mergers occur in stars.

Editorial extensions

If this is right

Merger-prone progenitors can be identified from the helium-burning phase, so pre-supernova models can be screened without evolving them all the way to collapse.
The odd-Z enhancement in Sc, K, and P provides a chemical fingerprint for recognising C-O merger ejecta in metal-poor stars and in galactic chemical evolution.
If mergers are required to match K and Sc at $[\rm Fe/H] < -3$, then yields from single non-merging massive stars alone are incomplete for early-Universe enrichment.
Because binarity raises $X_{\rm C12}$ by stripping mass, binary stars should experience fewer C-O shell mergers than single stars.
The $^{44}$Ti produced in the merger may contribute to the still-debated Galactic $^{44}$Ti budget.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

If the thresholds survive across different input physics, the roughly 50% success rate inside the box points to a hidden second trigger, such as convective boundary mixing or three-dimensional entrainment, that one-dimensional models do not capture.
The same $M_{\rm CO}$--$X_{\rm C12}$ screening could be applied to classify other convective-reactive events, such as neon-oxygen mergers, in existing model grids.
A systematic one-at-a-time variation of the $^{12}$C(α,γ)$^{16}$O rate and the convective criterion would convert the empirical box into a calibrated predictor with quantified uncertainty.
The grey-box criterion could be used to estimate what fraction of the first stellar generation must have undergone mergers to reproduce the observed $[\rm K/Mg]$ and $[\rm Sc/Mg]$ spread in extremely metal-poor stars.

Original abstract

In their final stages before undergoing a core-collapse supernova, massive stars may experience mergers between internal shells where carbon (C) and oxygen (O) are consumed as fuels for nuclear burning. This interaction, known as a C-O shell merger, can dramatically alter the internal structure of the star, leading to peculiar nucleosynthesis and potentially influencing the supernova explosion and the propagation of the subsequent supernova shock. Our understanding of the frequency and consequences of C-O shell mergers remains limited. This study aims to identify for the first time early diagnostics in the stellar structure which will lead to C-O shell mergers in more advanced stages. We also assess their role in shaping the chemical abundances in the most metal poor stars of the Galaxy. We analyze a set of 209 of stellar evolution models available in the literature, with different initial progenitor masses and metallicities. We then compare the nucleosynthetic yields from a subset of these models with the abundances of odd-Z elements in metal-poor stars. We find that the occurrence of C-O shell mergers in stellar models can be predicted with good approximation based on the outcomes of the central He burning phase, specifically, from the CO core mass ($\rm M_{CO}$) and the $\rm ^{12}C$ central mass fraction ($\rm X_{C12}$): 90$\%$ of models with a C-O merger have $\rm X_{C12}< 0.277$ and $\rm M_{CO}< 4.90 M_{\odot}$, with average values $\rm M_{CO} = 4.02 M_{\odot}$ and $\rm X_{C12}= 0.176$. Additionally, we confirm that the Sc-rich and K-rich yields from models with C-O mergers would solve the long-standing underproduction of these elements in massive stars. Our results emphasize the crucial role of C-O shell mergers in enriching the interstellar medium, particularly in the production of odd-Z elements.

The compiled record

The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

Compiled by classifier-1.13.0 via TypeSafe API, question bank abstract-p1-20260923, 2026-09-23: 1 request, 7,835 input tokens.

What the abstract itself states, as probabilities: claims first 0.88 · states limitation 0.30 · human participants 0.01 · controlled comparison 0.12 · randomized assignment 0.01 · states quantitative result 0.99 · compares with prior results 0.40 · mentions code or data availability 0.03.

The abstract, sentence by sentence

arXiv listing abstract v1. Results and the main claim are underlined; show every role.

In their final stages before undergoing a core-collapse supernova, massive stars may experience mergers between internal shells where carbon (C) and oxygen (O) are consumed as fuels for nuclear burning. This interaction, known as a C-O shell merger, can dramatically alter the internal structure of the star, leading to peculiar nucleosynthesis and potentially influencing the supernova explosion and the propagation of the subsequent supernova shock. Our understanding of the frequency and consequences of C-O shell mergers remains limited. This study aims to identify for the first time early diagnostics in the stellar structure which will lead to C-O shell mergers in more advanced stages. We also assess their role in shaping the chemical abundances in the most metal poor stars of the Galaxy. We analyze a set of 209 of stellar evolution models available in the literature, with different initial progenitor masses and metallicities. We then compare the nucleosynthetic yields from a subset of these models with the abundances of odd-Z elements in metal-poor stars. We find that the occurrence of C-O shell mergers in stellar models can be predicted with good approximation based on the outcomes of the central He burning phase, specifically, from the CO core mass ($\rm M_{CO}$) and the $\rm ^{12}C$ central mass fraction ($\rm X_{C12}$): 90$\%$ of models with a C-O merger have $\rm X_{C12}< 0.277$ and $\rm M_{CO}< 4.90 M_{\odot}$, with average values $\rm M_{CO} = 4.02 M_{\odot}$ and $\rm X_{C12}= 0.176$. Additionally, we confirm that the Sc-rich and K-rich yields from models with C-O mergers would solve the long-standing underproduction of these elements in massive stars. Our results emphasize the crucial role of C-O shell mergers in enriching the interstellar medium, particularly in the production of odd-Z elements.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#	sentence	role	the authors' own work	states the main conclusion	strength
s0	In their final stages before undergoing a core-collapse supernova, massive stars may experience mergers between internal shells where carbon (C) and oxygen (O) are consumed as fuels for nuclear burning.	background 1.00	0.04	0.02	hedged possibility 1.00
s1	This interaction, known as a C-O shell merger, can dramatically alter the internal structure of the star, leading to peculiar nucleosynthesis and potentially influencing the supernova explosion and the propagation of the subsequent supernova shock.	background 1.00	0.05	0.05	hedged possibility 0.67
s2	Our understanding of the frequency and consequences of C-O shell mergers remains limited.	gap 1.00	0.05	0.02	asserted 0.99
s3	This study aims to identify for the first time early diagnostics in the stellar structure which will lead to C-O shell mergers in more advanced stages.	contribution 1.00	0.35	0.04	asserted 0.67
s4	We also assess their role in shaping the chemical abundances in the most metal poor stars of the Galaxy.	contribution 1.00	0.50	0.03	unclear 0.55
s5	We analyze a set of 209 of stellar evolution models available in the literature, with different initial progenitor masses and metallicities.	method 0.99	0.78	0.02	asserted 0.96
s6	We then compare the nucleosynthetic yields from a subset of these models with the abundances of odd-Z elements in metal-poor stars.	method 0.96	0.92	0.03	asserted 0.67
s7	We find that the occurrence of C-O shell mergers in stellar models can be predicted with good approximation based on the outcomes of the central He burning phase, specifically, from the CO core mass ($\rm M_{CO}$) and the $\rm ^{12}C$ central mass fraction ($\rm X_{C12}$): 90$\%$ of models with a C-O merger have $\rm X_{C12}< 0.277$ and $\rm M_{CO}< 4.90 M_{\odot}$, with average values $\rm M_{CO} = 4.02 M_{\odot}$ and $\rm X_{C12}= 0.176$.	result 1.00	0.96	0.70	asserted 1.00
s8	Additionally, we confirm that the Sc-rich and K-rich yields from models with C-O mergers would solve the long-standing underproduction of these elements in massive stars.	result 0.96	0.89	0.17	asserted 0.95
s9	Our results emphasize the crucial role of C-O shell mergers in enriching the interstellar medium, particularly in the production of odd-Z elements.	interpretation 1.00	0.77	0.53	asserted 1.00

What kind of paper the classifier reports this is: simulation study 0.96 · evidence from analysis of existing data 0.84.

What was examined, and what was not

sources read

arXiv listing abstract v1

not examined

full text
figures and tables
references and citing sentences
relations to other papers

levels run

P abstract

not run

S sections
T body sentences
C citations
R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

Figures

**Figure 1.** The CO core mass (MCO) versus the central 12C mass fraction abundance (XC12) at the end of central He burning phase. The different colors identify the different set of models (see side legend) where RAU Rauscher et al. (2002); PGN Pignatari et al. (2016); SIE Sieverding et al. (2018); RIT Ritter et al. (2018b); L&C Limongi, M. & Chieffi, A. (2018); BRI Brinkman et al. (2019, 2021); LIM Limongi et al. (2024); RLC Roberti et al. (2024a); ROB Roberti et al. (2024b); KEP Jeena et al. (2024). Different symbols identify different initial masses (see top legend). Models with and without a…

**Figure 2.** Comparison between the abundances before (dashed lines) and after the C-O shell merger (solid lines) in the RIT 15 M⊙ model at solar metallicity (see Ritter et al. 2018b, for a detailed description of the model). The upper panel shows the effect of the merger on the major fuels. The lower panels show instead the effect of the merger on some key C- and O-burning products and selected odd-Z isotopes (see text). The vertical dotted lines represent the location of the edges of the shells before the C-O shell merger. The light grey area is the region modified by the merger, the dark…

**Figure 4.** The [K/Mg] (upper panel) and [Sc/Mg] (lower panel) versus the initial metallicity. The adopted solar reference is from Asplund et al. (2009). The different colored labels identify each set of models (see bottom legend): RAU Rauscher et al. (2002); NOM Nomoto et al. (2013); RIT Ritter et al. (2018b); L&C Limongi, M. & Chieffi, A. (2018); PUSH Ebinger et al. (2020); ROB Roberti et al. (2024b); RLC Roberti et al. (2024a); KEP Jeena et al. (2024). Different symbols identify different initial masses (see top legend). Models with and without a C-O shell merger are represented by a filled…

**Figure 5.** The [K/Mg] versus [Sc/Mg] ratios from those models selected from

Showing 4 of the paper's 5 figures. See all figures in the PDF ↗ Figures reproduced from arXiv:2504.18867 by the authors.

References

Works cited (25)

[1]

Abohalima, A. & Frebel, A. 2018, The Astrophysical Journal Supplement Series, 238, 36 Aerts, C. 2021, Reviews of Modern Physics, 93, 015001 Aerts, C., Thoul, A., Daszy´nska, J., et al. 2003, Science, 300, 1926 Ananna, C., Barbieri, L., Boeltzig, A., et al. 2024, Universe, 10, 228 Anders, E. & Grevesse, N. 1989, Geochim. Cosmochim. Acta, 53, 197 Andrassy, ...

View on Pith 2018
[2]

Models with a C-O shell merger have XC12 and MCO in boldface. Set Reference Code M ini (M⊙) Z ini Vini (km s−1) X C12 MCO (M⊙) ROB Roberti et al. (2024b) FRANEC 15.00 0.000e +00 0 3.62e-01 2.96 ROB Roberti et al. (2024b) FRANEC 15.00 0.000e +00 150 1.89e-01 4.07 ROB Roberti et al. (2024b) FRANEC 15.00 0.000e +00 300 1.29e-01 4.19 ROB Roberti et al. (2024b...

View on Pith 2024
[3]

stars taken from the JINAbase database Abohalima & Frebel (2018) (as detailed in Table C.1). The full database contains 121 stars with [K/Mg] and [Sc /Mg] observations, with initial metallicity in the range −4.12 ≤ [Fe/H] ≤ −1.51. More specifically, the data extracted from JINAbase is from Roederer et al. (2010); Cohen et al. (2013); Roederer et al. (2014...

View on Pith 2018
[4]

MESA 15.00 1.400e-02 0 3.23e-01 3.41 BRI Brinkman et al. (2019,

View on Pith 2019
[5]

MESA 20.00 1.400e-02 0 2.92e-01 5.66 BRI Brinkman et al. (2019,

View on Pith 2019
[6]

MESA 25.00 1.400e-02 0 2.62e-01 8.13 BRI Brinkman et al. (2019,

View on Pith 2019
[7]

MESA 10.00 1.400e-02 150 3.32e-01 1.58 BRI Brinkman et al. (2019,

View on Pith 2019
[8]

MESA 15.00 1.400e-02 150 3.11e-01 3.54 BRI Brinkman et al. (2019,

View on Pith 2019
[9]

MESA 20.00 1.400e-02 150 2.86e-01 5.83 BRI Brinkman et al. (2019,

View on Pith 2019
[10]

MESA 25.00 1.400e-02 150 2.71e-01 8.06 BRI Brinkman et al. (2019,

View on Pith 2019
[11]

MESA 10.00 1.400e-02 300 3.12e-01 1.84 BRI Brinkman et al. (2019,

View on Pith 2019
[12]

MESA 15.00 1.400e-02 300 3.13e-01 4.04 BRI Brinkman et al. (2019,

View on Pith 2019
[13]

MESA 20.00 1.400e-02 300 2.80e-01 6.62 BRI Brinkman et al. (2019,

View on Pith 2019
[14]

MESA 25.00 1.400e-02 300 2.63e-01 8.63 SIE Sieverding et al. (2018) KEPLER 15.00 1.400e-02 0 2.25e-01 2.24 SIE Sieverding et al. (2018) KEPLER 20.00 1.400e-02 0 2.15e-01 3.69 SIE Sieverding et al. (2018) KEPLER 25.00 1.400e-02 0 1.89e-01 5.39 RAU Rauscher et al. (2002) KEPLER 15.00 2.000e-02 0 2.00e-01 2.80 RAU Rauscher et al. (2002) KEPLER 20.00 2.000e-0...

View on Pith 2018
[15]

The adopted 12C+12C rate is instead the same for all the models and it is the one provided by Caughlan & Fowler (1988). We refer the reader to the cited papers for a more detailed description of each set of models. The models with a C-O shell merger are listed in Table A.1. A.1. The KEPLER models (RAU, SIE, KEP) We considered models calculated with the KE...

View on Pith 1988
[19]

spanning a wide range of initial rotation velocity (from 0 to 800 km s−1). All but two of the rotating 15 M⊙ models undergo C-O shell mergers. A.4. MESA models (RIT , BRI) We include two sets of models calculated with the MESA code Paxton et al. (2018). The RIT set Ritter et al. (2018b) includes massive star models of 12, 15, 20, 25 M⊙, at 5 different met...

View on Pith 2018
[20]

includes non-rotating and rotating massive star models at solar metallicity with M ini between 10 and 80 M⊙ and vini = 0, 150, and 300 km s−1, cal- culated up to the collapse of the Fe core. Again, we only consid- ered models up to 25 M⊙ (i.e., 10, 15, 20, and 25 M⊙). The con- vective boundaries are determined using the Ledoux criterion, with overshooting...

View on Pith 2002
[21]

Models with a C-O shell merger have [K/Mg] and [Sc/Mg] in boldface. Set Reference M ini (M⊙) Z ini Vini (km s−1) [K /Mg] [Sc /Mg] ROB Roberti et al. (2024b) 25.00 3.236e-08 0 -0.93 -1.44 ROB Roberti et al. (2024b) 25.00 3.236e-07 0 -0.71 -1.28 ROB Roberti et al. (2024b) 15.00 3.236e-06 0 -0.85 -1.62 ROB Roberti et al. (2024b) 25.00 0.000e +00 0 -1.25 -1.8...

View on Pith 2024
[25]

Simbad Identifier Ref a [Fe/H] [K /Mg] [Sc /Mg] 2MASS_J00061720 + 1057419 LI15a -3.26 0.07 -0.65 2MASS_J01090507− 0443211 ROE14b -3.57 0.00 -0.58 2MASS_J01265856 + 0135153 LI15a -3.57 0.13 -0.63 2MASS_J03173604− 1517227 ROE14b -3.06 0.04 -0.47 2MASS_J04121388− 1205050 ROE14b -3.31 0.15 -0.51 2MASS_J11272694− 2352056 ROE14b -3.36 -0.29 -0.61 2MASS_J1557301...

View on Pith 2013
[1993]

presented in Pignatari et al. (2016) (PGN), computed using the GENEC stellar evolutionary code Eggenberger et al. (2008). The evolution of these models is calculated up to the end of central Si burning phase, while the birth of the Si burning shell and the pre-collapse phase are not included. For this reason, we do not know if these models may experience ...

View on Pith 2016
[2013]

and the PUSH set (Curtis et al. 2019; Ebinger et al

View on Pith 2019
[2018]

and RLC (Roberti et al. 2024a) models are part of a large set of rotating massive stars, with initial masses between 13 and 120 M⊙ and spanning 5 different initial metallicities, [Fe /H] = 0.3, 0,−1,−2,−3. In this work, we considered only the models up to M ini≤ 25 M⊙ (i.e., Mini = 13, 15, 20, and 25 M⊙), at the three available rota- tion velocities (0, 1...

View on Pith 2002
[2020]

of zero (z-series) and 10−4Z⊙ metallicity (u-series). From the NOM set, we considered 6 CCSNe from progenitors with initial masses between 11 and 25 M ⊙ and 2 hypernova models with initial masses equal to 20 and 25 M ⊙. From the PUSH set we con- sidered 12 models of the u-series, with initial masses between 11 and 25 M⊙, and 13 models of the z-series, wit...

View on Pith 2020
[2021]

MESA 10.00 1.400e-02 0 3.78e-01 1.52 BRI Brinkman et al. (2019,

View on Pith 2019
[2024]

in- cludes models at solar metallicity in the range between 7 and 12 M⊙. Since we are interested in the CCSN progenitor evolution, we consider only the models that evolve to the formation of a Fe core, corresponding to models from M ini = 9.22 M⊙. In this set, the convective borders are determined according to the Ledoux criterion in the H-rich layers and...

View on Pith 2013

Forward citations

Cited by 3 Pith papers

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A Framework for Analysing Nebular-Phase JWST Supernova Spectra with Application to Type Ic SN 2024aecx
astro-ph.HE 2026-10 conditional novelty 7.0 of 10

A new analytic framework plus a grid of 112 spectral models lets one derive ejecta masses, ionisation fractions, temperatures, zone filling factors, and line optical depths from a single nebular JWST mid-infrared supe...
The physics of deep-interior convective shell boundaries in a massive pre-supernova star: Internal gravity wave mixing at the $N^2$ peak
astro-ph.SR 2026-09 conditional novelty 6.0 of 10

Convection-driven internal gravity waves, not overshoot or entrainment, dominate the mixing at the carbon-shell boundary of a pre-supernova 25 solar mass star, eroding the N-squared peak by about 40 percent within hours.
Electromagnetic Probes of the Supernova Engine
astro-ph.HE 2026-09 accept novelty 2.0 of 10

A comprehensive review of the observational and theoretical landscape of electromagnetic probes of core-collapse supernova explosions.

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1 arXiv paper cite this in 5 sentences

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The C–O shell merger is a phenomenon observed in several 1D stellar evolution simulations [ref] and has also been studied with multi-dimensional simulations of convective shells in massive stars [ref] .

Production of heavy $\alpha$-elements and $^{44}$Ti in Cas A: comparison to abundances from 1D core-collapse supernova models and evidence for Carbon-Oxygen shell mergers · Introduction · 0.88

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[1] [1]

Abohalima, A. & Frebel, A. 2018, The Astrophysical Journal Supplement Series, 238, 36 Aerts, C. 2021, Reviews of Modern Physics, 93, 015001 Aerts, C., Thoul, A., Daszy´nska, J., et al. 2003, Science, 300, 1926 Ananna, C., Barbieri, L., Boeltzig, A., et al. 2024, Universe, 10, 228 Anders, E. & Grevesse, N. 1989, Geochim. Cosmochim. Acta, 53, 197 Andrassy, ...

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[2] [2]

Models with a C-O shell merger have XC12 and MCO in boldface. Set Reference Code M ini (M⊙) Z ini Vini (km s−1) X C12 MCO (M⊙) ROB Roberti et al. (2024b) FRANEC 15.00 0.000e +00 0 3.62e-01 2.96 ROB Roberti et al. (2024b) FRANEC 15.00 0.000e +00 150 1.89e-01 4.07 ROB Roberti et al. (2024b) FRANEC 15.00 0.000e +00 300 1.29e-01 4.19 ROB Roberti et al. (2024b...

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[3] [3]

stars taken from the JINAbase database Abohalima & Frebel (2018) (as detailed in Table C.1). The full database contains 121 stars with [K/Mg] and [Sc /Mg] observations, with initial metallicity in the range −4.12 ≤ [Fe/H] ≤ −1.51. More specifically, the data extracted from JINAbase is from Roederer et al. (2010); Cohen et al. (2013); Roederer et al. (2014...

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[4] [4]

MESA 15.00 1.400e-02 0 3.23e-01 3.41 BRI Brinkman et al. (2019,

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[5] [5]

MESA 20.00 1.400e-02 0 2.92e-01 5.66 BRI Brinkman et al. (2019,

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[6] [6]

MESA 25.00 1.400e-02 0 2.62e-01 8.13 BRI Brinkman et al. (2019,

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[7] [7]

MESA 10.00 1.400e-02 150 3.32e-01 1.58 BRI Brinkman et al. (2019,

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[8] [8]

MESA 15.00 1.400e-02 150 3.11e-01 3.54 BRI Brinkman et al. (2019,

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[9] [9]

MESA 20.00 1.400e-02 150 2.86e-01 5.83 BRI Brinkman et al. (2019,

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[10] [10]

MESA 25.00 1.400e-02 150 2.71e-01 8.06 BRI Brinkman et al. (2019,

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[11] [11]

MESA 10.00 1.400e-02 300 3.12e-01 1.84 BRI Brinkman et al. (2019,

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[12] [12]

MESA 15.00 1.400e-02 300 3.13e-01 4.04 BRI Brinkman et al. (2019,

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[13] [13]

MESA 20.00 1.400e-02 300 2.80e-01 6.62 BRI Brinkman et al. (2019,

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[14] [14]

MESA 25.00 1.400e-02 300 2.63e-01 8.63 SIE Sieverding et al. (2018) KEPLER 15.00 1.400e-02 0 2.25e-01 2.24 SIE Sieverding et al. (2018) KEPLER 20.00 1.400e-02 0 2.15e-01 3.69 SIE Sieverding et al. (2018) KEPLER 25.00 1.400e-02 0 1.89e-01 5.39 RAU Rauscher et al. (2002) KEPLER 15.00 2.000e-02 0 2.00e-01 2.80 RAU Rauscher et al. (2002) KEPLER 20.00 2.000e-0...

View on Pith 2018

[15] [15]

The adopted 12C+12C rate is instead the same for all the models and it is the one provided by Caughlan & Fowler (1988). We refer the reader to the cited papers for a more detailed description of each set of models. The models with a C-O shell merger are listed in Table A.1. A.1. The KEPLER models (RAU, SIE, KEP) We considered models calculated with the KE...

View on Pith 1988

[16] [19]

spanning a wide range of initial rotation velocity (from 0 to 800 km s−1). All but two of the rotating 15 M⊙ models undergo C-O shell mergers. A.4. MESA models (RIT , BRI) We include two sets of models calculated with the MESA code Paxton et al. (2018). The RIT set Ritter et al. (2018b) includes massive star models of 12, 15, 20, 25 M⊙, at 5 different met...

View on Pith 2018

[17] [20]

includes non-rotating and rotating massive star models at solar metallicity with M ini between 10 and 80 M⊙ and vini = 0, 150, and 300 km s−1, cal- culated up to the collapse of the Fe core. Again, we only consid- ered models up to 25 M⊙ (i.e., 10, 15, 20, and 25 M⊙). The con- vective boundaries are determined using the Ledoux criterion, with overshooting...

View on Pith 2002

[18] [21]

Models with a C-O shell merger have [K/Mg] and [Sc/Mg] in boldface. Set Reference M ini (M⊙) Z ini Vini (km s−1) [K /Mg] [Sc /Mg] ROB Roberti et al. (2024b) 25.00 3.236e-08 0 -0.93 -1.44 ROB Roberti et al. (2024b) 25.00 3.236e-07 0 -0.71 -1.28 ROB Roberti et al. (2024b) 15.00 3.236e-06 0 -0.85 -1.62 ROB Roberti et al. (2024b) 25.00 0.000e +00 0 -1.25 -1.8...

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[19] [25]

Simbad Identifier Ref a [Fe/H] [K /Mg] [Sc /Mg] 2MASS_J00061720 + 1057419 LI15a -3.26 0.07 -0.65 2MASS_J01090507− 0443211 ROE14b -3.57 0.00 -0.58 2MASS_J01265856 + 0135153 LI15a -3.57 0.13 -0.63 2MASS_J03173604− 1517227 ROE14b -3.06 0.04 -0.47 2MASS_J04121388− 1205050 ROE14b -3.31 0.15 -0.51 2MASS_J11272694− 2352056 ROE14b -3.36 -0.29 -0.61 2MASS_J1557301...

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[20] [1993]

presented in Pignatari et al. (2016) (PGN), computed using the GENEC stellar evolutionary code Eggenberger et al. (2008). The evolution of these models is calculated up to the end of central Si burning phase, while the birth of the Si burning shell and the pre-collapse phase are not included. For this reason, we do not know if these models may experience ...

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[21] [2013]

and the PUSH set (Curtis et al. 2019; Ebinger et al

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[22] [2018]

and RLC (Roberti et al. 2024a) models are part of a large set of rotating massive stars, with initial masses between 13 and 120 M⊙ and spanning 5 different initial metallicities, [Fe /H] = 0.3, 0,−1,−2,−3. In this work, we considered only the models up to M ini≤ 25 M⊙ (i.e., Mini = 13, 15, 20, and 25 M⊙), at the three available rota- tion velocities (0, 1...

View on Pith 2002

[23] [2020]

of zero (z-series) and 10−4Z⊙ metallicity (u-series). From the NOM set, we considered 6 CCSNe from progenitors with initial masses between 11 and 25 M ⊙ and 2 hypernova models with initial masses equal to 20 and 25 M ⊙. From the PUSH set we con- sidered 12 models of the u-series, with initial masses between 11 and 25 M⊙, and 13 models of the z-series, wit...

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[24] [2021]

MESA 10.00 1.400e-02 0 3.78e-01 1.52 BRI Brinkman et al. (2019,

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[25] [2024]

in- cludes models at solar metallicity in the range between 7 and 12 M⊙. Since we are interested in the CCSN progenitor evolution, we consider only the models that evolve to the formation of a Fe core, corresponding to models from M ini = 9.22 M⊙. In this set, the convective borders are determined according to the Ledoux criterion in the H-rich layers and...

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