This study investigates radiative proton capture reactions in light nuclei such as [9B- 7Li, - 7Be], which are crucial in stellar nucleosynthesis and energy production. The Woods-Saxon potential model was employed to describe nuclear interactions, and the Schrödinger equation was solved to determine bound and continuum state wave functions accurately. Astrophysical S-factors and reaction cross-sections were calculated at low energies characteristic of stellar environments, accounting for nuclear resonance effects that significantly enhance reaction probabilities. Radiative proton capture reactions, of the form A(p,γ)B, are fundamental processes in nuclear astrophysics. They are the primary mechanism for synthesizing elements in both hydrostatic and explosive stellar environments. he formation of ⁷Li and ⁷Be is a key outcome of the Big Bang. The reaction ³He(α,γ)⁷Be is the primary source of ⁷Be, which later decays to ⁷Li. Understanding the ⁷Be system is thus crucial for predicting the primordial lithium abundance. The theoretical results show strong agreement with experimental data, validating the model's reliability. These findings provide precise inputs for refining nuclear reaction rates in stellar evolution models, thereby improving predictions of elemental synthesis and energy generation in stars.

We investigate low-energy astrophysical S factors for reactions proceeding through the Be 8 compound system with entrance channels p + Li 7 , n + Be 7 , and d + Li 6 . Using the same microscopic many-channel three-cluster framework as in our previous study of the high-lying Be 8 spectrum, we calculate S ( E ) for Li 7 ( p , α ) He 4 , Be 7 ( n , α ) He 4 , Be 7 ( n , p ) Li 7 , Li 6 ( d , α ) He 4 , Li 6 ( d , p ) Li 7 , and Li 6 ( d , n ) Be 7 in the energy range relevant for primordial and stellar nucleosynthesis. For the mirror reactions Li 7 ( p , α ) He 4 and Be 7 ( n , α ) He 4 , as well as for Be 7 ( n , p ) Li 7 the calculated S factors reproduce both the absolute scale and the low-energy trends of the experimental data within their quoted uncertainties, whereas the absolute S factors for the deuteron-induced channels on Li 6 are underestimated at low energy, consistent with the shifted Li 6 + d threshold and the absence of a broad subthreshold 2 + structure in the present implementation. A partial-wave analysis identifies the dominant J π contributions in each channel and relates them to specific Be 8 resonances, while demonstrating that cluster polarization, previously shown to be crucial for the Be 8 spectrum, is likewise essential for the normalization and energy dependence of several S factors. Evaluating S ( E ) at appropriate Gamow energies, we obtain a hierarchy of reaction channels that quantifies the relative importance of neutron- and deuteron-induced processes for the production and destruction of Li 7 and Be 7 .

Magnesium isotopic ratios offer valuable insights into stellar nucleosynthesis and Galactic chemical evolution, particularly in distinguishing between contributions from supernovae and asymptotic giant branch (AGB) stars. These isotopes are accessible through MgH molecular features in cool stellar atmospheres, yet their measurement remains challenging across a range of spectral types. We aim to assess the reliability of MgH spectral regions for extracting magnesium isotopic ratios ( 24 Mg, ^25Mg, and ^ 26 Mg) in stars spanning spectral types from M to G, and to evaluate the consistency of these measurements with nucleosynthetic expectations. We applied an analysis pipeline using spectrum synthesis to derive isotopic ratios, validated using three well-studied reference stars, to a sample of five additional dwarf and giant stars. Individual MgH molecular band regions were analysed to determine their sensitivity to isotopic variation. Europium (Eu) and barium (Ba) abundances were also measured to explore potential correlations with magnesium isotopic ratios as r and s process proxies, respectively. There are ten wavelength regions for which MgH have previously been investigated. Our study determined that seven of these regions were the most reliable for extracting isotopic information. Other regions exhibited limited sensitivity between stellar type and parameters. The Mg isotope ratios ( 24 Mg:^25Mg:^26Mg) obtained in this work include: HD 11695-81:7:12; HD 18884-81:7:12; HD 18907-69:9:23; HD 22049-71:16:13; HD 23249-66:13:22; HD 128621-67:17:16; HD 10700-78:10:12; and HD 100407-65:10:25. Comparison of europium (Eu) abundances with the three magnesium isotopes revealed strong correlations. The strongest correlation was with ^24Mg. Note that ^24Mg is predominantly produced by hydrostatic α$ capture in massive stars, a process that precedes the r process responsible for Eu production. In contrast, barium (Ba) abundances showed no significant correlation with ^25Mg and $^ 26 Mg, despite their shared AGB origin.With removal of the effect of metallicity similar results were found. Our results demonstrate that selected MgH regions can reliably measure magnesium isotopes in cool stars, providing a reproducible framework for future studies of stellar nucleosynthesis and galactic chemical evolution.

Abstract Barium stars are unusually enriched in barium ([Ba/Fe] ≥ 1.0 dex) and not predicted by current Galactic chemical evolution models. Previous observations of barium stars have found evidence that they form through mass transfer from a companion asymptotic giant branch (AGB) star or through radiative levitation. The chemical abundance and kinematic information of barium stars may help constrain AGB stellar nucleosynthesis, binary star evolution, and internal evolutionary processes that affect surface abundances. Using ∼450,000 stars from the Galactic Archaeology with Hermes (GALAH) survey, we identify nearly 3000 new barium-rich stars and separate them into hot ( T eff > 6000 K) and cool ( T eff < 6000 K) populations. Crossmatching with Gaia Data Release 3, we find that 47.7% of our barium stars within 1 kpc have an elevated renormalized unit weight error (RUWE; ≥1.4), compared to 16.3% of a comparable sample of the GALAH field, suggesting multiplicity plays an important role in the formation of both populations of barium stars. A subset of hot barium stars exhibit low RUWEs (RUWE < 1.2) and [ α /Fe] < −0.2, supporting radiative levitation as an origin as well. We determine Galactic memberships using both kinematics and chemistry and find that barium stars exist in the thin disk, thick disk, and halo though they are slightly more prevalent at lower metallicities. Overall, we show evidence for barium stars produced by mass transfer and for those produced by radiative levitation, with both formation mechanisms occurring ubiquitously across the Galaxy.

We analyze the elastic $α$-$^{12}$C scattering including the contribution of resonance states below the $p$-$^{15}$N breakup threshold energy. We use the cluster effective field theory in which scattering amplitude is expanded in terms of the effective range expansion parameters for the angular momentum states from $l=0$ to $l=6$. The amplitude contains 37 parameters, which are determined by fitting to 11 392 differential cross section data points of the elastic $α$-$^{12}$C scattering. To optimize the fitting process, we implement the differential evolution (DE) algorithm, which performs a global search over the high-dimensional parameter space and consistently converges to the same minimum $χ^{2}$ value across independent runs, suggesting proximity to the global minimum within the explored domain. In parallel, the Markov chain Monte Carlo (MCMC) method is used to crosscheck the DE results and to estimate the parameter uncertainties. The best fit yields $χ^{2}/N\!\simeq\!6.2$ for the elastic scattering data. Using the determined 37 parameters, we calculate the differential cross sections and the phase shifts of the elastic $α$-$^{12}$C scattering and compare the results with experimental data and those of an $R$-matrix analysis. Our result of the cross section agrees with the experimental data as accurately as an $R$-matrix analysis. The results demonstrate that the cluster effective field theory, combined with global optimization and uncertainty quantification based on DE-MCMC methods, provides a reliable and systematic framework for applications to low energy phenomena relevant to stellar evolution and nucleosynthesis.

Recent measurements performed by the LUNA(Laboratory for Underground Nuclear Astrophysics) collaboration between 2019 and 2024 have provided the most precise direct determinations to date of several key reaction rates in the NeNa cycle, specifically the 20Ne(p,γ)21Na and the 22Ne(p,γ)23Na reactions, as well as its bridge to the MgAl cycle, i.e., the 23Na(p,γ)24Mg reaction. Despite their improved accuracy, these updated rates are not yet consistently incorporated into widely used nuclear reaction network compilations. We explore the astrophysical impact of adopting the new LUNA rates by performing nucleosynthesis calculations, focusing on the case of 26Al nucleosynthesis and considering four different stellar environments: low-mass AGB stars, massive stars, very massive stars and core-collapse supernovae. Our results show substantial sensitivity of 26Al production to the revised rates. In the AGB model, the surface 26Al abundance decreases by up to 30%, while in the massive star model, the 26Al abundance in the C-burning shell increases by 51%. In contrast, the impact on both the 26Al yields ejected by very massive stars and on the explosive nucleosynthesis in the supernova model is negligible. These findings have direct implications for galactic chemical evolution, the global budget of 26Al, and theoretical predictions of the 60Fe/26Al ratio, which will be critically tested by forthcoming γ-ray observations from missions such as the Compton Spectrometer and Imager (COSI).

The Research Topic "Strong and Weak Interactions in Compact Stars" provides a broad overview of recent advances in the study of the physics of compact stars. The contributions span nuclear and quark matter equations of state, weak interaction rates in dense matter, nucleosynthesis, rotational and thermal effects in neutron stars, and the interpretation of observational constraints. Combined they shed light on the progress achieved and the challenges that remain in constructing a coherent, multi-scale description of compact stars.Several articles focus on the equation of state (EoS) of dense matter, which remains a central uncertainty in neutron star physics. Tong et al. provide a concise review of relativistic Brueckner-Hartree-Fock theory formulated in full Dirac space, emphasizing recent technical advances beyond common angleaveraging approximations and their implications for neutron star structure. Reinforcing this microscopic perspective, Sammaruca and Ajagbonna argue for the use of state-of-the-art ab initio nuclear and neutron matter calculations as a robust baseline for high-density extrapolations. By combining these with causality, maximum-mass constraints, and speed-of-sound-guided parametrizations, they delineate allowed regions of the EoS and present associated predictions for neutron star cooling.The connection between nuclear experiments, astrophysical observations, and dense-matter theory is explored further by Burgio et al., who investigate correlations between the density dependence of the symmetry energy and neutron skin thickness measurements in finite nuclei, in light of recent CREX and PREX results. By analyzing a broad ensemble of microscopic and phenomenological EoS models consistent with neutron star mass and tidal deformability constraints, this work highlights emerging tensions between laboratory data and current theoretical descriptions of the nuclear EoS.Strong interactions at even higher densities, where deconfined quark matter may appear, are addressed in several contributions. Alford et al. study the bulk viscosity of warm, dense, neutrino-transparent quark matter in the two-flavor color-superconducting (2SC) phase driven by weak interaction β-decays (Urca reactions). Using an extended SU(3) Nambu-Jona-Lasinio model, they demonstrate a pronounced sensitivity of bulk viscosity and damping timescales to vector interactions, with important implications for the dissipation of density oscillations in merging compact stars. In a complementary phenomenological approach, Kourmpetis et al. explore whether color-flavor locked (CFL) quark matter, modeled by the MIT bag model, can explain the observed properties of two compact stars, which have similar low masses but potentially different radii. The study explores two scenarios: absolutely stable strange quark matter and hybrid stars, determining acceptable ranges for the superconducting gap and bag parameter in each case. This work illustrates how observational constraints can discriminate between different realizations of quark matter in compact stars.Weak interactions play a crucial role in shaping the thermal and chemical evolution of compact stars and their progenitors. Kabir et al. investigate β-decay properties of medium-mass nuclei relevant for stellar environments, combining relativistic mean-field calculations of nuclear deformation with pn-QRPA evaluations of Gamow-Teller strength and stellar weak rates. The resulting rates, systematically larger than those obtained in alternative models, are of direct relevance for simulations of late-stage stellar evolution and nucleosynthesis. On a much larger astrophysical scale, Blaschke et al. address the long-standing puzzle of the near-universality of heavy-element abundances. Using a nonequilibrium freeze-out framework and a phenomenological characterization of r-process distributions, they show how weak-interaction-driven dynamics and density fluctuations can naturally account for both the typical abundance pattern and its observed variations.The macroscopic manifestations of dense-matter microphysics are further explored through studies of gravity and rotation. Cai and Li derive equation-of-state-independent constraints on supradense matter by analyzing the scaled Tolman-Oppenheimer-Volkoff equations in general relativity. This work reveals tight bounds on the pressure-energy-density ratio and establishes direct links between observable neutron star properties and the dense matter EoS, without reliance on specific nuclear models. Farrell et al. examine the effects of differential rotation and finite temperature on neutron star structure and stability, using finite-temperature relativistic Brueckner-Hartree-Fock equations of state. The results demonstrate that differential rotation has a significant impact on maximum masses and rotational instabilities, while temperature plays a comparatively minor role within the explored range. These findings are particularly relevant for interpreting post-merger remnants.Combined, the articles collected in this Research Topic illustrate the rich and multifaceted role of strong and weak interactions in compact stars, from the microphysics of nuclei and quarks to the global structure and dynamics of general-relativistic, rotating objects. They underscore the necessity of combining microscopic theory, phenomenological modeling, and observational input to make progress in this field. We hope that this collection will serve both as a highlight of current advances and as a stimulus for future work aimed at unraveling the physics of matter under extreme conditions.

Abstract Isotopes of chromium (Cr) and other iron-group elements are predominantly made in the inner shells of supernovae and are later reprocessed via the slow neutron capture process ( s -process) in asymptotic giant branch (AGB) stars. Nucleosynthetic models of low-mass, solar metallicity AGB stars yield significant overproduction of 54 Cr ( δ 54 Cr values ∼ +160‰) with limited variations in other Cr isotopes, relative to solar system values. Here we report Cr, C, and N isotopic compositions of 16 individual presolar silicon carbide (SiC) grains of the KJG series (1.5–3 μ m) from the Murchison (CM2.0) meteorite. 12 C/ 13 C and 14 N/ 15 N ratios of the 14 mainstream SiC grains range from 29 to 108 and 259 to 7800, respectively. These C, N isotopic compositions are consistent with their formation in red giant and AGB stars. Two types of AB grains could have originated in a J-type C-star (AB2) and a type-II supernova (AB). The majority of mainstream grains display close-to-solar Cr isotopic compositions, indicating the Cr was not significantly processed within their parent AGB stars. A mainstream SiC grain with relatively high 54 Cr enrichment of δ 54 Cr ∼ 700‰ likely originated from a very low metallicity parent star based on the stellar nucleosynthesis model (FRUITY). We consider the plausible origin of this grain from Galactic halo stars, migration from the outer Galactic disk, and other scenarios. Elemental Cr concentrations of the grains vary from ∼1 to 9 ppm, with 75% of the grains displaying an average concentration of ∼2 ppm. Cr concentration does not vary significantly with grain size, suggesting that the Cr in the SiC grains condensed during grain formation and was not implanted at a later stage.

Abstract Measuring cross-sections of nuclear reactions, such as the so-called "Holy Grail" reaction, 12 C(α, γ) 16 O, is essential for understanding stellar nucleosynthesis but presents significant challenges due to extremely low cross sections. Key challenges include significant energy loss as ions penetrate the target material, limiting measurements to thin target layers. To overcome these obstacles, we propose a novel method, the in-target Energy LOss Compensating (eLOC), specifically designed for gas targets, which utilizes a gas-filled magnetic field and accelerating electric fields to compensate for ion energy loss in targets. Simulations show that this approach significantly enhances the effective target thickness by over 140 times in the case of the "Holy Grail" reaction with inverse kinematic setup. This eLOC method may provide a powerful new tool for obtaining critical data in nuclear astrophysics, thereby advancing our understanding of stellar nucleosynthesis and the origins of elements in the universe, as well as benefiting other related fields like isotope production.

The radiative proton capture reactions 12C(p, γ)13N, 14N(p, γ)15O, and 17O(p, γ)18F have been investigated within the framework of a direct capture model employing Woods - Saxon potentials. These reactions play a fundamental role in hydrogen burning through the carbon-nitrogen-oxygen (CNO) cycles in stellar interiors. Nuclear structure inputs constrained by experimental data have been used to calculate astrophysical S factors and scattering phase shifts. The calculated results show good agreement with available measurements, accurately reproducing both non-resonant contributions and narrow resonance features in the 12C(p, γ)13N and 17O(p, γ)18F reactions. The rate-limiting behavior of the 14N(p, γ)15O reaction in the CNO-I cycle has also been described with satisfactory precision. The findings provide improved inputs for stellar nucleosynthesis modeling and contribute to the understanding of low-energy nuclear capture processes relevant to astrophysics.

This paper introduces LRPayne, a novel algorithm designed for the efficient determination of stellar parameters and chemical abundances from low-resolution optical spectra, with a primary focus on data from large-scale galactic surveys such as WEAVE. LRPayne employs a model-driven approach, utilising a fully connected artificial neural network (ANN), trained on a library of 70,000 synthetic stellar spectra generated using iSpec with 1D model atmospheres and the Turbospectrum synthesis code. We trained the network to predict normalized flux given stellar labels (T_̊m eff, log(g), Fe/H , v_mic, v_max, and v,sin,i, plus 24 individual elemental abundances). We subsequently derived stellar parameters from observed spectra by finding the best-fit synthetic spectrum from the ANN using a ̧hi^2 minimisation technique. The method operates on spectra degraded to a resolution of R=5000 covering the 4200-6900 Å wavelength range. Internal accuracy tests on synthetic spectra show a median interpolation error of less than 0.13 $%$ for 90 $%$ of the validation sample. The method accurately recovers most of the input labels from synthetic spectra, even at a signal-to-noise ratio (S/N) of 20, with some expected challenges for elements such as Li, K, and N. Validation on the observed spectra of 25 Gaia FGK benchmark stars and 42 metal-poor stars reveals good agreement with the literature values. For the stellar parameters, the mean differences are 22±87 K for T_ . Abundances for elements such as Na, Mg, Si, and most Fe-peak elements (Cr, Ni, V, and Sc) are well-recovered. We note challenges for oxygen, manganese in metal-rich giants, aluminium in metal-poor stars and dwarfs, and deriving log g in hot metal-poor dwarfs, partly due to non-local thermodynamic equilibrium effects and line characteristics. eff​, 0.19±0.23 dex for log(g), and 0.01±0.17 dex for Fe/H LRPayne demonstrates the possibility of extracting precise stellar parameters and chemical abundances from a large number of low-resolution spectra. Its strong performance across different kinds of stars makes it well-suited for current and future large surveys. The abundance results from LRPayne will be very useful for studying stellar nucleosynthesis and the chemical evolution of our Galaxy on a large scale.

Abstract In massive stars (initial mass of ≳9 M ⊙ ), the weak s - (slow neutron capture) process produces elements between Fe and Zr, enriching the Galaxy with these elements through core-collapse supernova explosions. The weak s -process nucleosynthesis is driven by neutrons produced in the 22 Ne( α , n ) 25 Mg reaction during convective He core and C shell burning. The yields of heavy elements thus depend on the 22 Ne( α , n ) 25 Mg and the competitive 22 Ne( α , γ ) 26 Mg reaction rates, which are dominated by several narrow-resonance reactions. While the accuracy of these rates has been under debate for decades, recent experimental efforts, including ours, drastically reduced these uncertainties. In this work, we use a set of 280 massive star nucleosynthesis models calculated using different 22 Ne( α , n ) 25 Mg and 22 Ne( α , γ ) 26 Mg rates and a galactic chemical evolution (GCE) study to probe their impact on the weak s -process elemental abundances in the Galaxy. The GCE was computed with the OMEGA+ code, using the new sets of stellar yields with different 22 Ne+ α rates. From GCE, we find that these rates are causing up to 0.45 dex of variations in the [Cu/Fe], [Ga/Fe], and [Ge/Fe] ratios predicted at solar metallicity. The greatest impact on the stellar nucleosynthesis and GCE results derives from uncertainties in the ( α , n ) strength ( ωγ ( α , n ) ) of the E x = 11.32 MeV resonance. We show that variations observed in the GCE calculations for weak s -process elements become negligibly smaller than dispersions found in observations once the ωγ ( α , n ) is accurately determined within the uncertainty of 10%–20% (typically reported experimental errors for the resonance) in future nuclear physics experiments.

Supernovae are very energetic and interesting events in the universe. They play a key role in stellar evolution, nucleosynthesis, and cosmic structure formation. In recent years, multi-messenger astronomy has become more important. It combines observations from electromagnetic (EM) radiation and gravitational waves (GWs). This paper looks at the synergies between EM and GW observations of supernovae. First, the author introduces the theoretical background. This includes supernova types, mechanisms, and the signals they produce. Then, it talks about observational techniques. These include ground-based and space-based telescopes, and GW detectors like LIGO and Virgo. Also, this paper discusses how EM and GW data can be combined. This gives a more complete understanding of supernova dynamics, progenitor stars, and compact object formation. Challenges, like sensitivity limits and theoretical uncertainties, are also highlighted. Finally, he considers future prospects. These include next-generation detectors, artificial intelligence, and finding new astrophysical phenomena. This review shows the importance of international collaboration and technological advancement. It will help unlock the mysteries of supernovae through multi-messenger astronomy.

Abstract This paper is in memory of Roberto Gallino, a long-time collaborator on questions of neutron sources and neutron-induced reactions in stellar nucleosynthesis. We therefore discuss a topic that was of great interest to him, the correlation between neutron sources that provide the neutron flux for the production of heavy elements in the s -process and neutron poison reactions that reduce the number of neutrons in the stellar environment. Neutron poisons play a role in all s -process environments, such as the final phase of core helium burning of massive stars or the carbon pocket in hydrogen-helium intershell environment of low-mass AGB stars, originally proposed by Gallino and his co-workers more than 40 years ago. This paper will argue that neutron poison reactions serve as a neutron storage mechanism through which neutron sources can be fueled to provide a delayed neutron release.

The <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mo>(</a:mo> <a:mi mathvariant="normal">n</a:mi> <a:mo>,</a:mo> <a:mo> </a:mo> <a:mi>γ</a:mi> <a:mo>)</a:mo> </a:math> cross section of silver is crucial for the nucleosynthesis process of nuclear astrophysics, the design of silver-indium-cadmium absorber rod in the nuclear reactors, and neutron resonance capture analysis for determining the elemental and isotopic composition of cultural heritage. The high-precision <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"> <c:mi>Ag</c:mi> <c:mo>(</c:mo> <c:mi mathvariant="normal">n</c:mi> <c:mo>,</c:mo> <c:mo> </c:mo> <c:mi>γ</c:mi> <c:mo>)</c:mo> </c:math> cross section was measured from 1 eV to 1 MeV at the Back-n facility of the Chinese Spallation Neutron Source using the time-of-flight method and pulse height weighting technique. The resonance parameters were accurately extracted in the resolved resonance region by the multilevel multichannel <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"> <e:mi>R</e:mi> </e:math> -matrix code . The code was used to describe the average cross sections in the unresolved resonance region, and the Maxwellian-averaged cross sections (MACSs) of <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"> <f:mrow> <f:mmultiscripts> <f:mi mathvariant="normal">Ag</f:mi> <f:mprescripts/> <f:none/> <f:mn>107</f:mn> </f:mmultiscripts> </f:mrow> </f:math> and <h:math xmlns:h="http://www.w3.org/1998/Math/MathML"> <h:mrow> <h:mmultiscripts> <h:mi mathvariant="normal">Ag</h:mi> <h:mprescripts/> <h:none/> <h:mn>109</h:mn> </h:mmultiscripts> </h:mrow> </h:math> were further given in the 5–100 keV range. The MACS values at <j:math xmlns:j="http://www.w3.org/1998/Math/MathML"> <j:mrow> <j:mi>k</j:mi> <j:mi>T</j:mi> <j:mo>=</j:mo> <j:mn>30</j:mn> <j:mo> </j:mo> <j:mi>keV</j:mi> </j:mrow> </j:math> for <k:math xmlns:k="http://www.w3.org/1998/Math/MathML"> <k:mrow> <k:mmultiscripts> <k:mi mathvariant="normal">Ag</k:mi> <k:mprescripts/> <k:none/> <k:mn>107</k:mn> </k:mmultiscripts> </k:mrow> </k:math> <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"> <m:mo>(</m:mo> <m:mn>887</m:mn> <m:mo> </m:mo> <m:mo>±</m:mo> <m:mo> </m:mo> <m:mn>89</m:mn> <m:mo> </m:mo> <m:mi>mb</m:mi> <m:mo>)</m:mo> </m:math> and <n:math xmlns:n="http://www.w3.org/1998/Math/MathML"> <n:mrow> <n:mmultiscripts> <n:mi mathvariant="normal">Ag</n:mi> <n:mprescripts/> <n:none/> <n:mn>109</n:mn> </n:mmultiscripts> </n:mrow> </n:math> <p:math xmlns:p="http://www.w3.org/1998/Math/MathML"> <p:mo>(</p:mo> <p:mn>903</p:mn> <p:mo> </p:mo> <p:mo>±</p:mo> <p:mo> </p:mo> <p:mn>90</p:mn> <p:mo> </p:mo> <p:mi>mb</p:mi> <p:mo>)</p:mo> </p:math> are slightly higher than the recommended values in the Karlsruhe Astrophysical Database of Stellar Nucleosynthesis.

Supernovae (SNe) are among the most energetic and transient events in the universe, offering crucial insights into stellar evolution, nucleosynthesis, and cosmic expansion. Optical observations have historically played a central role in the discovery, classification, and physical interpretation of SNe. In this review, we summarize recent progress in the optical study of SNe, with a focus on advancements in time-domain surveys and photometric and spectroscopic follow-up strategies. High-cadence optical monitoring is pivotal in capturing the diverse behaviors of SNe, from early-time emission to late-phase decline. Leveraging data from ARIES telescopes and national/international collaborations, we systematically investigate various SN types, including Type Iax, IIP/L, IIb, IIn/Ibn and Ib/c events. Our analysis includes light curve evolution and spectral diagnostics, providing insights into early emission signatures (e.g., shock breakout), progenitor systems, explosion mechanisms, and circumstellar medium (CSM) interactions. Through detailed case studies, we demonstrate the importance of both early-time and nebular-phase observations in constraining progenitor and CSM properties. This comprehensive approach underscores the importance of coordinated global efforts in time-domain astronomy to deepen our understanding of SN diversity. We conclude by discussing the challenges and opportunities for future optical studies in the era of wide-field observatories such as the Vera C. Rubin Observatory (hereafter Rubin), with an emphasis on detection strategies, automation, and rapid-response capabilities.

Fluorine abundance in stars is a sensitive indicator of the physical conditions and processes occurring within their interiors. Recent extrapolated results on the ^{19}F(p,αγ)^{16}O fluorine destruction cross section suggested an increase of the astrophysical factor by several orders of magnitude at astrophysical energies, with profound implications for our understanding of stellar evolution and nucleosynthesis. We have indirectly measured the ^{19}F(p,αγ)^{16}O cross section using the Trojan horse method, fully covering astrophysical energies with no need of extrapolations. The strength of the 11keV resonance was extracted and a significant reduction of the reaction rate was determined, compared to previous studies. The analysis of the astrophysical impact suggests that our measurement challenges existing predictions about fluorine and heavier elements' abundances, reigniting unresolved questions in the field.

The discovery of a new, e+e− reaction channel in deuteron-deuteron (DD) fusion at very low energies might have major implications for understanding primordial and stellar nucleosynthesis, where electron-positron reaction channels are typically not considered. It could also enable research on metal hydride fusion, potentially paving the way for the design and construction of next-generation fusion energy sources. Following the first experimental indications of electron emission, we present here an extensive experimental study confirming emission of high-energy electrons from DD reaction at very low energy. A simultaneous use of Si charged particle detectors of different thicknesses and large-volume NaI(Tl) and HPGe detectors has allowed the determination of the branching ratios between emitted protons, neutrons, and e+e− pairs for deuteron energies down to 5 keV. The high-energy positrons could be unambiguously detected by their bremsstrahlung spectra and annihilation radiation, supported by the eant4 Monte Carlo simulations. The theoretical calculations, based on a destructive interference between the threshold resonance and the known broad resonance in He4, agree very well with experimentally observed increase of branching ratios for lowering projectile energies. The partial width of the threshold resonance for the internal e+e− pair creation should be at least 10 times larger than that of the proton channel.

This work presents a preliminary study aimed at optimizing an experimental setup for future fast neutron cross section measurements, with a focus on the inelastic neutron scattering reaction 12C(n, n')12C*. This reaction is of interest for stellar nucleosynthesis since it is expected to dominate the increase of the triple-α reaction rate to the ground state of 12C. To support the development of an effective setup, we have examined inelastic neutron scattering to the excited states of 12C up to 10.3 MeV at a laboratory angle of 60°. Monte Carlo simulations were performed using MCNP6.2 to model an experimental configuration involving a DT neutron generator producing 14.16 MeV neutrons. These simulations were used to evaluate and benchmark the detection efficiency of our system and to investigate key factors influencing the measurement accuracy, including target thickness, detector thickness, the presence of air (lack of vacuum), and the multiple scattering effects. The simulations provided a detailed understanding of the various contributions to the overall measurement, allowing us to optimize key parameters in preparation for high-precision experiments. Experimental and simulated time-of-flight (TOF) spectra were compared and good agreement was obtained for the 4.44 MeV state but revealed significant discrepancies for the 7.654 MeV excitation state (the Hoyle state), 9.63 MeV and 10.3 MeV. This suggests that the contribution of the Hoyle and higher states may have been underestimated in published data and highlights a need for further justifications.

Chemical properties of stellar populations are a key observable that can be used to shed light on the assembly history of galaxies across cosmic time. In this study, we investigate the distribution and origin of chemical elements in different stellar components of simulated Milky Way-like galaxies in relation to their mass assembly history, stellar age, and metallicity. Using a sample of 23 simulated galaxies from the Auriga project, we analysed the evolution of heavy elements produced by stellar nucleosynthesis. To study the chemical evolution of the stellar halo, bulge, and warm (thick) and cold (thin) discs of the model galaxies, we applied a decomposition method to characterise the distribution of chemical elements at z=0 and traced back their origin. Our findings indicate that each stellar component has a distinctive chemical trend despite galaxy-to-galaxy variations. Specifically, stellar haloes are α-enhanced relative to other components, representing the oldest populations, with mathrm Fe/H ∼ -0.6 and a high fraction of ex situ stars of ∼50%. They are followed by the warm (mathrm Fe/H ∼ -0.1) and cold (mathrm Fe/H ∼ 0) discs, with in situ fractions of ∼90% and ∼95%, respectively. Alternatively, bulges are mainly formed in situ but host more diverse stellar populations, with Fe/H abundance extending over ∼1 dex around the solar value. We conclude that one of the main drivers shaping the chemical properties of the galactic components in our simulations is the age-metallicity relation. The bulges are the least homogeneous component of the sample, as they present different levels of contribution from young stars in addition to the old stellar component. Conversely, the cold discs appear very similar in all chemical properties, despite important differences in their typical formation times. Finally, we find that a significant fraction of stars in the warm discs were in the cold disc component at birth. We discuss the possible connections of this behaviour with the development of bars and interactions with satellites.