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1. Production of Radioactive ²² Na in Core-collapse Supernovae: The Ne-E(L) Component in Presolar Grains and Its Possible Consequences on Supernova Observations

   https://doi.org/10.3847/1538-4357/adef4c  

   Pignatari, Marco; Amari, Sachiko; Hoppe, Peter; Fryer, C; Jones, S; Psaltis, A; Laird, A M; Herwig, F; Roberti, L; Siegert, Thomas; et al (August 2025, The Astrophysical Journal)

   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. 

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2. New Wolf–Rayet wind yields and nucleosynthesis of Helium stars

   https://doi.org/10.1093/mnras/stae1853  

   Higgins, Erin_R; Vink, Jorick_S; Hirschi, Raphael; Laird, Alison_M; Sander, Andreas_A_C (August 2024, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT Strong metallicity-dependent winds dominate the evolution of core He-burning, classical Wolf–Rayet (cWR) stars, which eject both H and He-fusion products such as $$^{14}$$N, $$^{12}$$C, $$^{16}$$O, $$^{19}$$F, $$^{22}$$Ne, and $$^{23}$$Na during their evolution. The chemical enrichment from cWRs can be significant. cWR stars are also key sources for neutron production relevant for the weak s-process. We calculate stellar models of cWRs at solar metallicity for a range of initial Helium star masses (12–50 $$\rm M_{\odot }$$), adopting recent hydrodynamical wind rates. Stellar wind yields are provided for the entire post-main sequence evolution until core O-exhaustion. While literature has previously considered cWRs as a viable source of the radioisotope $$^{26}$$Al, we confirm that negligible $$^{26}$$Al is ejected by cWRs since it has decayed to $$^{26}$$Mg or proton-captured to $$^{27}$$Al. However, in Paper I, we showed that very massive stars eject substantial quantities of $$^{26}$$Al, among other elements including N, Ne, and Na, already from the zero-age-main-sequence. Here, we examine the production of $$^{19}$$F and find that even with lower mass-loss rates than previous studies, our cWR models still eject substantial amounts of $$^{19}$$F. We provide central neutron densities (N$$_{n}$$) of a 30 $$\rm M_{\odot }$$ cWR compared with a 32 $$\rm M_{\odot }$$ post-VMS WR and confirm that during core He-burning, cWRs produce a significant number of neutrons for the weak s-process via the $$^{22}$$Ne($$\alpha$$,n)$$^{25}$$Mg reaction. Finally, we compare our cWR models with observed [Ne/He], [C/He], and [O/He] ratios of Galactic WC and WO stars. 

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3. Aluminum–Silica Core–Shell Nanoparticles via Nonthermal Plasma Synthesis

   https://doi.org/10.3390/nano15030237  

   Cameron, Thomas; Klause, Bailey; Loh, Kristine Q; Kortshagen, Uwe R (February 2025, Nanomaterials)

   Aluminum nanoparticles (Al NPs) are interesting for energetic and plasmonic applications due to their enhanced size-dependent properties. Passivating the surface of these particles is necessary to avoid forming a native oxide layer, which can degrade energetic and optical characteristics. This work utilized a radiofrequency (RF)-driven capacitively coupled argon/hydrogen plasma to form surface-modified Al NPs from aluminum trichloride (AlCl3) vapor and 5% silane in argon (dilute SiH4). Varying the power and dilute SiH4 flow rate in the afterglow of the plasma led to the formation of varying nanoparticle morphologies: Al–SiO2 core–shell, Si–Al2O3 core–shell, and Al–Si Janus particles. Scanning transmission electron microscopy with a high-angle annular dark-field detector (STEM-HAADF) and energy-dispersive X-ray spectroscopy (EDS) were employed for characterization. The surfaces of the nanoparticles and sample composition were characterized and found to be sensitive to changes in RF power input and dilute SiH4 flow rate. This work demonstrates a tunable range of Al–SiO2 core–shell nanoparticles where the Al-to-Si ratio could be varied by changing the plasma parameters. Thermal analysis measurements performed on plasma-synthesized Al, crystalline Si, and Al–SiO2 samples are compared to those from a commercially available 80 nm Al nanopowder. Core–shell particles exhibit an increase in oxidation temperature from 535 °C for Al to 585 °C for Al–SiO2. This all-gas-phase synthesis approach offers a simple preparation method to produce high-purity heterostructured Al NPs. 

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4. Solubility of Rock in Steam Atmospheres of Planets

   https://doi.org/10.3847/0004-637X/824/2/103  

   Fegley, Bruce; Jacobson, Nathan S.; Williams, K. B.; Plane, J. M.; Schaefer, L.; Lodders, Katharina (June 2016, Astrophysical journal)

   Extensive experimental studies show that all major rock-forming elements (e.g., Si, Mg, Fe, Ca, Al, Na, K) dissolve in steam to a greater or lesser extent. We use these results to compute chemical equilibrium abundances of rocky-element-bearing gases in steam atmospheres equilibrated with silicate magma oceans. Rocky elements partition into steam atmospheres as volatile hydroxide gases (e.g., Si(OH)4, Mg(OH)2, Fe(OH)2, Ni(OH)2, Al(OH)3, Ca(OH)2, NaOH, KOH) and via reaction with HF and HCl as volatile halide gases (e.g., NaCl, KCl, CaFOH, CaClOH, FAl(OH)2) in much larger amounts than expected from their vapor pressures over volatile-free solid or molten rock at high temperatures expected for steam atmospheres on the early Earth and hot rocky exoplanets. We quantitatively compute the extent of fractional vaporization by defining gas/magma distribution coefficients and show that Earth's subsolar Si/Mg ratio may be due to loss of a primordial steam atmosphere. We conclude that hot rocky exoplanets that are undergoing or have undergone escape of steam-bearing atmospheres may experience fractional vaporization and loss of Si, Mg, Fe, Ni, Al, Ca, Na, and K. This loss can modify their bulk composition, density, heat balance, and interior structure. 

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5. VapoRock: Thermodynamics of Vaporized Silicate Melts for Modeling Volcanic Outgassing and Magma Ocean Atmospheres

   https://doi.org/10.3847/1538-4357/acbcc7  

   Wolf, Aaron S.; Jäggi, Noah; Sossi, Paolo A.; Bower, Dan J. (April 2023, The Astrophysical Journal)

   Abstract Silicate vapors play a key role in planetary evolution, especially dominating early stages of rocky planet formation through outgassed magma ocean atmospheres. Our open-source thermodynamic modeling software “VapoRock” combines the MELTS liquid model with gas-species properties from multiple thermochemistry tables. VapoRock calculates the partial pressures of 34 gaseous species in equilibrium with magmatic liquid in the system Si–Mg–Fe–Al–Ca–Na–K–Ti–Cr–O at desired temperatures and oxygen fugacities (fO₂, or partial pressure of O₂). Comparison with experiments shows that pressures and melt-oxide activities (which vary over many orders of magnitude) are reproduced to within a factor of ∼3, consistent with measurement uncertainties. We also benchmark the model against a wide selection of igneous rock compositions including bulk silicate Earth, predicting elemental vapor abundances that are comparable to (Na, Ca, and Al) or more realistic than (K, Si, Mg, Fe, and Ti) those of the closed-source MAGMA code (with maximum deviations by factors of 10–300 for K and Si). Vapor abundances depend critically on the activities of liquid components. The MELTS model underpinning VapoRock was calibrated and extensively tested on natural igneous liquids. In contrast, MAGMA’s liquid model assumes ideal mixtures of a limited set of chemically simplified pseudospecies, which only roughly approximates the nonideal compositional interactions typical of many-component natural silicate melts. Finally, we explore how relative abundances of SiO and SiO₂provide a spectroscopically measurable proxy for oxygen fugacity in devolatilized exoplanetary atmospheres, potentially constrainingfO₂in outgassed exoplanetary mantles. 

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