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Context.Although current observations indicate that there are two distinct sequences of disk stars in the [α/M] versus [M/H] parameter space, further complexity is evident in the chemical makeup of the Milky Way and consequently suggests a complicated evolutionary history. Aims.We developed two-infall galactic chemical evolution (GCE) models consistent with the Galactic chemical map. Methods.We obtained new GCE models simulating the chemical evolution of the Milky Way, as constrained by a golden sample of 394 000 stellar abundances of the Milky Way Mapper survey from data release 19 of SDSS-V. The separation between the chemical thin and thick disks was defined using [Mg/M]. We used the chemical evolution environmentOMEGA+combined with Levenberg-Marquardt (LM) and bootstrapping algorithms for the optimization and error estimation. We simulated the entire Galactic disk and considered six galactocentric regions, allowing for a more detailed analysis of the formation of the inner, middle, and outer Galaxy. We investigated the evolution ofα, odd-Z, and iron-peak elements, covering 15 species altogether. Results.The chemical thin and thick disks are separated by Mg observations, which the otherα-elements show similar trends with, while odd-Z species demonstrate different patterns as functions of metallicity. In the inner Galactic disk regions, the locus of the low-Mg sequence is gradually shifted toward higher metallicity, while the high-Mg phase is less populated. The best-fit GCE models show a well-defined peak in the rate of the infalling matter as a function of the Galactic age, confirming a merger event about 10 Gyr ago. We show that the timescale of gas accretion, the exact time of the second infall and the ratio between the surface mass densities associated with the second infall event and the formation event vary with the distance from the Galactic center. According to the models, the disk was assembled within a timescale of (0.32±0.02) Gyr during a primary formation phase, followed by an increasing accretion rate over a (0.55±0.06) Gyr-timescale and a relaxation phase that lasted (2.86±0.70) Gyr, with a second peak seen for the infall rate at (4.13±0.19) Gyr. Conclusions.Our best Galaxy evolution models are consistent with an inside-out formation scenario of the Milky Way disk and in agreement with the findings of recent chemodynamical simulations. 

Abstract Presolar graphite grains carry the isotopic signatures of their parent stars. A significant fraction of presolar graphites show isotopic abundance anomalies relative to solar for elements such as O, Si, Mg, and Ca, which are compatible with nucleosynthesis in core-collapse supernovae (CCSNe). Therefore, they must have condensed from CCSN ejecta before the formation of the Sun. Their most puzzling abundance signature is the²²Ne-enriched component Ne-E(L), interpreted as the effect of the radioactive decay of²²Na (T_1/2= 2.6 yr). Previous works have shown that if H is ingested into the He shell and not fully destroyed before the explosion, the CCSN shock in the He-shell material produces large amounts of²²Na. Here we focus on such CCSN models, showing a radioactive²⁶Al production compatible with grain measurements, and analyze the conditions of²²Na nucleosynthesis. In these models,²²Na is mostly made in the He shell, with a total ejected mass varying between 2.6 × 10⁻³M_⊙and 1.9 × 10⁻⁶M_⊙. We show that such²²Na may already impact the CCSN light curve 500 days after the explosion, and at later stages it can be the main source powering the CCSN light curve for up to a few years before⁴⁴Ti decay becomes dominant. Based on the CCSN yields above, the 1274.53 keVγ-ray flux due to²²Na decay could be observable for years after the first CCSN light is detected, depending on the distance. This makes CCSNe possible sites to detect a²²Naγ-ray signature consistently with the Ne-E(L) component found in presolar graphites. Finally, we discuss the potential contribution from²²Na decay to the Galactic positron annihilation rate. 

Context. The atmospheres of phosphorus-rich (P-rich) stars have been shown to contain between 10 and 100 times more P than our Sun. Given its crucial role as an essential element for life, it is especially necessary to uncover the origin of P-rich stars to gain insights into the still unknown nucleosynthetic formation pathways of P in our Galaxy. Aims. Our objective is to obtain the extensive chemical abundance inventory of four P-rich stars, covering a large range of heavy (Z > 30) elements. This characterization will serve as a milestone for the nuclear astrophysics community to uncover the processes that form the unique chemical fingerprint of P-rich stars. Methods. We performed a detailed 1D local thermodynamic equilibrium abundance analysis on the optical UVES spectra of four P-rich stars. The abundance measurements, complemented with upper-limit estimates, included 48 light and heavy elements. Our focus lay on the neutron-capture elements (Z > 30), in particular, on the elements between Sr and Ba, as well as on Pb, as they provide valuable constraints to nucleosynthesis calculations. In past works, we showed that the heavy-element observations from the first P-rich stars are not compatible with either classical s-process or r-process abundance patterns. In this work, we compare the obtained abundances with three different nucleosynthetic scenarios: a single i-process, a double i-process, and a combination of s- and i-processes. Results. We have performed the most extensive abundance analysis of P-rich stars to date, including the elements between Sr and Ba, such as Ag, which are rarely measured in any type of stars. We also estimated constraining upper limits for Cd I, In I, and Sn I. We found overabundances with respect to solar in the s-process peak elements, accompanied by an extremely high Ba abundance and slight enhancements in some elements between Rb and Sn. No global solution explaining all four stars could be found for the nucleosynthetic origin of the pattern. The model that produces the least number of discrepancies in three of the four stars is a combination of s- and i-processes, but the current lack of extensive multidimensional hydrodynamic simulations to follow the occurrence of the i-process in different types of stars makes this scenario highly uncertain. 

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 We run a three‐dimensional Galactic chemical evolution (GCE) model to follow the propagation of⁵³Mn (exclusively produced from type Ia supernovae, SNIa),⁶⁰Fe (exclusively produced from core‐collapse supernovae, CCSNe),¹⁸²Hf (exclusively produced from intermediate mass stars, IMSs), and²⁴⁴Pu (exclusively produced from neutron star mergers, NSMs). By comparing the predictions from our three‐dimensional GCE model to recent detections of⁵³Mn,⁶⁰Fe, and²⁴⁴Pu on the deep‐sea floor, we draw conclusions about their propagation in the interstellar medium. 

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 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 While modeling the galactic chemical evolution (GCE) of stable elements provides insights to the formation history of the Galaxy and the relative contributions of nucleosynthesis sites, modeling the evolution of short-lived radioisotopes (SLRs) can provide supplementary timing information on recent nucleosynthesis. To study the evolution of SLRs, we need to understand their spatial distribution. Using a three-dimensional GCE model, we investigated the evolution of four SLRs:⁵³Mn,⁶⁰Fe,¹⁸²Hf, and²⁴⁴Pu with the aim of explaining detections of recent (within the last ≈1–20 Myr) deposition of live⁵³Mn,⁶⁰Fe, and²⁴⁴Pu of extrasolar origin into deep-sea reservoirs. We find that core-collapse supernovae are the dominant propagation mechanism of SLRs in the Galaxy. This results in the simultaneous arrival of these four SLRs on Earth, although they could have been produced in different astrophysical sites, which can explain why live extrasolar⁵³Mn,⁶⁰Fe, and²⁴⁴Pu are found within the same, or similar, layers of deep-sea sediments. We predict that¹⁸²Hf should also be found in such sediments at similar depths. 

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.