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ABSTRACT We report isotope data for C, N, Al, Si, and S of 33 presolar SiC and Si3N4 grains (0.3–1.6 $$\mu$$m) of Type X, C, D, and N from the Murchison CM2 meteorite of likely core-collapse supernova (CCSN) origin which we discuss together with data of six SiC X grains from an earlier study. The isotope data are discussed in the context of hydrogen ingestion supernova (SN) models. We have modified previously used ad-hoc mixing schemes in that we considered (i) heterogeneous H ingestion into the He shell of the pre-SN star, (ii) a variable C-N fractionation for the condensation of SiC grains in the SN ejecta, and (iii) smaller mass units for better fine-tuning. With our modified ad-hoc mixing approach over small scales (0.2–0.4 M⊙), with major contributions from the O-rich O/nova zone, we find remarkably good fits (within a few per cent) for 12C/13C, 26Al/27Al, and 29Si/28Si ratios. The 14N/15N ratio of SiC grains can be well matched if variable C-N fractionation is considered. However, the Si3N4 isotope data point to overproduction of 15N in hydrogen ingestion CCSN models and lower C-N fractionation during SiC condensation than applied here. Our ad-hoc mixing approach based on current CCSN models suggests that the O-rich O/nova zone, which uniquely combines explosive H- and He-burning signatures, is favourable for SiC and Si3N4 formation. The effective range of C/O abundance variations in the He shell triggered by H ingestion events in the massive star progenitor is currently not well constrained and needs further investigation. 

Abstract A clear definition of the contribution from the slow neutron-capture process (s process) to the solar abundances between Fe and the Sr-Zr region is a crucial challenge for nuclear astrophysics. Robust s-process predictions are necessary to disentangle the contribution from other stellar processes producing elements in the same mass region. Nuclear uncertainties are affecting s-process calculations, but most of the needed nuclear input are accessible to present nuclear experiments or they will be in the near future. Neutron-capture rates have a great impact on the s process in massive stars, which is a fundamental source for the solar abundances of the lighter s-process elements heavier than Fe (weak s-process component). In this work we present a new nuclear sensitivity study to explore the impact on the s process in massive stars of 86 neutron-capture rates, including all the reactions between C and Si and between Fe and Zr. We derive the impact of the rates at the end of the He-burning core and at the end of the C-burning shell, where the$$^{22}$$ ${}^{22}$Ne($$\alpha $$ $\alpha$,n)$$^{25}$$ ${}^{25}$Mg reaction is is the main neutron source. We confirm the relevance of the light isotopes capturing neutrons in competition with the Fe seeds as a crucial feature of the s process in massive stars. For heavy isotopes we study the propagation of the neutron-capture uncertainties, finding a clear difference of the impact of Fe and Co isotope rates with respect to the rates of heavier stable isotopes. The local uncertainty propagation due to the neutron-capture rates at the s-process branching points is also considered, discussing the example of$$^{85}$$ ${}^{85}$Kr. The complete results of our study for all the 86 neutron-capture rates are available online. Finally, we present the impact on the weak s process of the neutron-capture rates included in the new ASTRAL library (v0.2). 

Neutron captures produce the vast majority of abundances of elements heavier than iron in the Universe. Beyond the classical slow ( s) and rapid ( r) processes, there is observational evidence for neutron-capture processes that operate at neutron densities in between, at different distances from the valley of β stability. Here, we review the main properties of the s process within the general context of neutron-capture processes and the nuclear physics input required to investigate it. We describe massive stars and asymptotic giant branch stars as the s-process astrophysical sites and discuss the related physical uncertainties. We also present current observational evidence for the s process and beyond, which ranges from stellar spectroscopic observations to laboratory analysis of meteorites. 

Abstract Many of the short-lived radioactive nuclei that were present in the early solar system can be produced in massive stars. In the first paper in this series, we focused on the production of²⁶Al in massive binaries. In our second paper, we considered rotating single stars; two more short-lived radioactive nuclei,³⁶Cl and⁴¹Ca; and the comparison to the early solar system data. In this work, we update our previous conclusions by further considering the impact of binary interactions. We used the MESA stellar evolution code with an extended nuclear network to compute massive (10–80M_⊙), binary stars at various initial periods and solar metallicity (Z= 0.014), up to the onset of core collapse. The early solar system abundances of²⁶Al and⁴¹Ca can be matched self-consistently by models with initial masses ≥25M_⊙, while models with initial primary masses ≥35M_⊙can also match³⁶Cl. Almost none of the models provide positive net yields for¹⁹F, while for²²Ne the net yields are positive from 30M_⊙and higher. This leads to an increase by a factor of approximately 4 in the amount of²²Ne produced by a stellar population of binary stars, relative to single stars. In addition, besides the impact on the stellar yields, our 10M_⊙primary star undergoing Case A mass transfer ends its life as a white dwarf instead of as a core-collapse supernova. This demonstrates that binary interactions can also strongly impact the evolution of stars close to the supernova boundary. 

Abstract Analysis of bulk meteorite compositions has revealed small isotopic variations due to the presence of material (e.g., stardust) that preserved the signature of nuclear reactions occurring in specific stellar sites. The interpretation of such anomalies provides evidence for the environment of the birth of the Sun, its accretion process, the evolution of the solar proto-planetary disk, and the formation of the planets. A crucial element of such interpretation is the comparison of the observed anomalies to predictions from models of stellar nucleosynthesis. To date, however, this comparison has been limited to a handful of model predictions. This is mostly because the calculated stellar abundances need to be transformed into a specific representation, which nuclear astrophysicists and stellar nucleosynthesis researchers are not familiar with. Here, we show in detail that this representation is needed to account for mass fractionation effects in meteorite data that can be generated both in nature and during instrumental analysis. We explain the required internal normalisation to a selected isotopic ratio, describe the motivations behind such representation more widely, and provide the tools to perform the calculations. Then, we present some examples considering two elements produced by the slow neutron-capture ( s ) process: Sr and Mo. We show which specific representations for the Sr isotopic composition calculated by s -process models better disentangle the nucleosynthetic signatures from stars of different metallicity. For Mo, the comparison between data and models is improved due to a recent re-analysis of the $$^{95}$$ 95 Mo neutron-capture cross section. 

ABSTRACT Certain types of silicon carbide (SiC) grains, e.g. SiC-X grains, and low density (LD) graphites are C-rich presolar grains that are thought to have condensed in the ejecta of core-collapse supernovae (CCSNe). In this work, we compare C, N, Al, Si, and Ti isotopic abundances measured in presolar grains with the predictions of 21 CCSN models. The impact of a range of SN explosion energies is considered, with the high energy models favouring the formation of a C/Si zone enriched in 12C, 28Si, and 44Ti. Eighteen of the 21 models have H ingested into the He-shell and different abundances of H remaining from such H-ingestion. CCSN models with intermediate to low energy (that do not develop a C/Si zone) cannot reproduce the 28Si and 44Ti isotopic abundances in grains without assuming mixing with O-rich CCSN ejecta. The most 28Si-rich grains are reproduced by energetic models when material from the C/Si zone is mixed with surrounding C-rich material, and the observed trends of the 44Ti/48Ti and 49Ti/48Ti ratios are consistent with the C-rich C/Si zone. For the models with H-ingestion, high and intermediate explosion energies allow the production of enough 26Al to reproduce the 26Al/27Al measurements of most SiC-X and LD graphites. In both cases, the highest 26Al/27Al ratio is obtained with H still present at XH ≈ 0.0024 in He-shell material when the SN shock is passing. The existence of H in the former convective He-shell points to late H-ingestion events in the last days before massive stars explode as a supernova. 

Abstract We report C, N, Mg-Al, Si, and S isotope data of six 1–3μm-sized SiC grains of Type X from the Murchison CM2 chondrite, believed to have formed in the ejecta of core-collapse supernova (CCSN) explosions. Their C, N, and Si isotopic compositions are fully compatible with previously studied X grains. Magnesium is essentially monoisotopic²⁶Mg which gives clear evidence for the decay of radioactive²⁶Al. Inferred initial²⁶Al/²⁷Al ratios are between 0.6 and 0.78 which is at the upper end of previously observed ratios of X grains. Contamination with terrestrial or solar system Al apparently is low or absent, which makes the X grains from this study particularly interesting and useful for a quantitative comparison of Al isotope data with predictions from supernova models. The consistently high²⁶Al/²⁷Al ratios observed here may suggest that the lower²⁶Al/²⁷Al ratios of many X grains from the literature are the result of significant Al contamination and in part also of an improper quantification of²⁶Al. The real dispersion of²⁶Al/²⁷Al ratios in X grains needs to be explored by future studies. The high observed²⁶Al/²⁷Al ratios in this work provide a crucial constraint for the production of²⁶Al in CCSN models. We explored different CCSN models, including both “classical” and H ingestion CCSN models. It is found that the classical models cannot account for the high²⁶Al/²⁷Al ratios observed here; in contrast, H ingestion models are able to reproduce the²⁶Al/²⁷Al ratios along with C, N, and Si isotopic ratios reasonably well. 

ABSTRACT The cosmic production of the short-lived radioactive nuclide 26Al is crucial for our understanding of the evolution of stars and galaxies. However, simulations of the stellar sites producing 26Al are still weakened by significant nuclear uncertainties. We re-evaluate the 26Al(n, p)26Mg, and 26Al(n, α)23Na ground state reactivities from 0.01 GK to 10 GK, based on the recent n_TOF measurement combined with theoretical predictions and a previous measurement at higher energies, and test their impact on stellar nucleosynthesis. We computed the nucleosynthesis of low- and high-mass stars using the Monash nucleosynthesis code, the NuGrid mppnp code, and the FUNS stellar evolutionary code. Our low-mass stellar models cover the 2–3 M⊙ mass range with metallicities between Z = 0.01 and 0.02, their predicted 26Al/27Al ratios are compared to 62 meteoritic SiC grains. For high-mass stars, we test our reactivities on two 15 M⊙ models with Z = 0.006 and 0.02. The new reactivities allow low-mass AGB stars to reproduce the full range of 26Al/27Al ratios measured in SiC grains. The final 26Al abundance in high-mass stars, at the point of highest production, varies by a factor of 2.4 when adopting the upper, or lower limit of our rates. However, stellar uncertainties still play an important role in both mass regimes. The new reactivities visibly impact both low- and high-mass stars nucleosynthesis and allow a general improvement in the comparison between stardust SiC grains and low-mass star models. Concerning explosive nucleosynthesis, an improvement of the current uncertainties between T9∼0.3 and 2.5 is needed for future studies. 

Abstract Type Ia supernova explosions (SN Ia) are fundamental sources of elements for the chemical evolution of galaxies. They efficiently produce intermediate-mass (withZbetween 11 and 20) and iron group elements—for example, about 70% of the solar iron is expected to be made by SN Ia. In this work, we calculate complete abundance yields for 39 models of SN Ia explosions, based on three progenitors—a 1.4M_⊙deflagration detonation model, a 1.0M_⊙double detonation model, and a 0.8M_⊙double detonation model—and 13 metallicities, with²²Ne mass fractions of 0, 1 × 10⁻⁷, 1 × 10⁻⁶, 1 × 10⁻⁵, 1 × 10⁻⁴, 1 × 10⁻³, 2 × 10⁻³, 5 × 10⁻³, 1 × 10⁻², 1.4 × 10⁻², 5 × 10⁻², and 0.1, respectively. Nucleosynthesis calculations are done using the NuGrid suite of codes, using a consistent nuclear reaction network between the models. Complete tables with yields and production factors are provided online at Zenodo:Yields (https://doi.org/10.5281/zenodo.8060323). We discuss the main properties of our yields in light of the present understanding of SN Ia nucleosynthesis, depending on different progenitor mass and composition. Finally, we compare our results with a number of relevant models from the literature. 

ABSTRACT Theoretical physical-chemical models for the formation of planetary systems depend on data quality for the Sun’s composition, that of stars in the solar neighbourhood, and of the estimated ’pristine’ compositions for stellar systems. The effective scatter and the observational uncertainties of elements within a few hundred parsecs from the Sun, even for the most abundant metals like carbon, oxygen and silicon, are still controversial. Here we analyse the stellar production and the chemical evolution of key elements that underpin the formation of rocky (C, O, Mg, Si) and gas/ice giant planets (C, N, O, S). We calculate 198 galactic chemical evolution (GCE) models of the solar neighbourhood to analyse the impact of different sets of stellar yields, of the upper mass limit for massive stars contributing to GCE (Mup) and of supernovae from massive-star progenitors which do not eject the bulk of the iron-peak elements (faint supernovae). Even considering the GCE variation produced via different sets of stellar yields, the observed dispersion of elements reported for stars in the Milky Way (MW) disc is not reproduced. Among others, the observed range of super-solar [Mg/Si] ratios, sub-solar [S/N], and the dispersion of up to 0.5 dex for [S/Si] challenge our models. The impact of varying Mup depends on the adopted supernova yields. Thus, observations do not provide a constraint on the Mup parametrization. When including the impact of faint supernova models in GCE calculations, elemental ratios vary by up to 0.1–0.2 dex in the MW disc; this modification better reproduces observations.