Stellar explosions and colliding neutron stars are significant sources of the chemical elements found in nature. While some astrophysical processes responsible for element creation are well-understood, others, like the rapid neutron capture process (r-process), remain challenging to study. These nucleosynthesis processes often involve reactions on short-lived radioactive isotopes, which can...
The trans-iron elements with atomic numbers 27 < Z < 52 are still not well
understood (Peterson et al. 2020, A&A, 638, A64). There is some evidence
for Ge to be classified rather as an iron-peak element than a neutron-capture
element. In particular, abundances of
Cobalt and Copper are of interest to elucidate their origin as
neutron capture elements on iron-group nuclei during He...
The s, i, and r processes are neutron-capture nucleosynthetic channels that occur at different neutron densities. Modern reaction network calculations follow these processes in great detail in models of stellar environments, but those calculations do not necessarily provide a full but straightforward quantitative accounting of the flow of abundance from one species to another. This talk will...
The technetium(Tc) -rich M stars reported in the literature
(Little-Marenin & Little 1979; Uttenthaler et al. 2013; Shetye et al. 2022) are
puzzling objects since no isotope of technetium has a half-life longer than a few
million years, and 99Tc, the longest-lived isotope along the s-process path, is
expected to be detected only in thermally-pulsing stars enriched with other
s-process...
Despite considerable progresses during the last decades, the origin of the elements heavier than iron is not yet fully understood. In addition to the slow (s) and rapid (r) neutron capture processes, an intermediate neutron capture process (i-process) is thought to exist at neutron densities intermediate between the s- and r-processes. The astrophysical site(s) hosting the i-process is (are)...
The neutron capture cross section of $^{64}$Ni is an important parameter in nuclear astrophysics to accurately simulate stellar nucleosynthesis and validate stellar models. $^{64}$Ni is among the seeds of the s-process and acts as an effective bottleneck for the production of the heavier nuclei in the s-process path. For this reason, its neutron capture cross section has been found to be one...
Binary Neutron Star mergers are a promising site for the nucleosynthesis of heavy elements via the r-process. This has been observationally confirmed with the detection of the kilonova AT2017gfo and the investigation of its light curves and spectra. While much work has been done to decode AT2017gfo signatures, the specific identifications of elements responsible for each spectral feature is...
The observation of kilonova AT2017gfo following the neutron star merger GW170817 [1] has provided compelling evidence for the production of r-process elements in these events. While recent spectral analyses have identified several elements in the ejecta [2,3,4], accurate abundance determinations remain challenging due to limitations in available atomic data, especially for modeling later...
GW170817 and SN1987A were the events of the century which opened a window to multi-messenger astronomy and astrophysics. There is a growing consensus that the MHD-Jet supernova and collapsar dominate the heavy r-element production over the entire history of cosmic evolution, and the neutron-star merger contribution delays due to cosmologically long time-delay for slow GW radiation [1,2]. We...
The stellar precursors of the protoplanetary disk defined the Solar System’s composition, a fundamental property that influenced the nature of the subsequent planetary system. The identity of the dominant stellar precursors, however, remains under investigation. Partial constraints have been inferred from nucleosynthetic isotope (i.e., genetic) anomalies in meteorites. Genetic anomalies are...
Despite the first direct evidence of r-process nucleosynthesis occurring in the merger of two neutron stars, the problem of the presence of one or more sites where the r-process can proceed is not settled. Depending on the merger rate and on the average ejecta amount, mergers involving neutron stars could explain the bulk of the r-process elements in the Galaxy. However, metal poor stars and...
Recent work using APOGEE stellar abundances have suggested that the Milky Way disk is well-mixed and chemically simple, with age, [Fe/H], and [Mg/Fe] predicting a star's detailed chemical profile to high precision. APOGEE notably lacks access to strong lines of neutron-capture elements which may experience a distinct trajectory of chemical evolution that can not be traced by the...
The origin of the heaviest elements is still a matter of debate. For the rapid neutron capture process (r-process), multiple sites have been proposed, e.g., neutron star mergers and (sub-classes) of supernovae. R -process elements have been measured in a large fraction of metal-poor stars. Galactic archaeology studies show that the r-process abundances among these stars vary by over 2 orders...
Blue straggler stars (BSSs) are thought to form from binary interactions, particularly mass transfer, mergers, and collisions. If a BSS forms from mass accreted from a thermally-pulsing asymptotic-giant-branch (AGB) star, it can bear distinctive surface abundance markers as a result of s-process nucleosynthesis that occurred in the evolved donor star. We present an abundance study of BSSs in...
Neutron detection sometimes plays a vital role in direct studies of astrophysically important reactions. In particular, the reaction 22Ne(a,n)25Mg is undergoing study using the SHADES array at the Belotti Ion Beam facility at Laboratori Nazionali del Gran Sasso. This reaction, and 13C(a,n)16O, is widely regarded to serve as a neutron fuel for the slow neutron capture (s-) process occurring in...
Charge-Exchange (CE) reactions are an important tool for studying the spin-isopin response of nuclei. They can be utilized to obtain information about interactions mediated by the weak nuclear force, such as β and electron capture decay. Using the proportionality between Gamow-Teller strength (B(GT)) and the CE differential cross section, B(GT) distributions can be extracted indirectly. Since...
Gaia BH3 is the third black hole that was discovered with in the early data release in Gaia DR4 due to the astrometric implication of a ~33 solar mass companion of a red giant. This red giant companion is an old metal-poor star that is likely a part of the Sequoia halo substructure. The possible production mechanisms for this binary system and the initial detection of Eu in this star (Gaia...
Neutron star mergers eject dense neutron rich material which are understood to be the primary sites for the production of many of the heavy elements in the universe via rapid neutron capture process, the r-process. There are several competing processes and reactions that determine the amount of heavy nuclei produced during this process, including the cooling of the material, neutron captures,...
The production of heavy elements beyond iron in the expanding ejecta of binary neutron star mergers (NSMs) provided evidence for the synthesis of lanthanides and possibly actinides through rapid neutron capture (r-process) nucleosynthesis. However, identifying specific atomic absorption and emission features in kilonova spectra to associate them with individual elements remains a significant...
The decreasing trend of the [Eu/Fe] feature caused by stars in the Large Magellanic Cloud (LMC) is followed by a nearly constant value; this trend is generally attributed to an onset of the delayed Fe release from type Ia supernovae (SNe), which is the same interpretation of the [$\alpha$/Fe] feature. However, this feature appears in the LMC at [Fe/H] of approximately -0.7, which is...
The determination of stellar ages remains one of the greatest challenges in astrophysics, as age cannot be directly measured. Advances over the last decade highlight the great potential of chemical clocks, particularly abundance ratios involving s-process and α- elements to estimate stellar ages with improved precision. For a sample of ~200 stars observed with the high-resolution spectrograph...
Nuclear weak-interaction processes play an important role in nucleosynthesis processes and late-stages of the evolution of stars. These processes are often modified due to the temperature and density conditions of the environment allowing for the appearance of novel decay channels normally not found under laboratory conditions. At the moderate conditions at which the s-process operates in AGB...
The chemo-kinematical properties of the Milky Way stellar halo contain the fossil records of our galaxy assembly history.
The Measuring at Intermediate Metallicity Neutron-Capture Elements (MINCE) project aims to provide high quality measurements of n-capture elements in halo stars at intermediate metallicity.
In the metallicity range -2.5 < [Fe/H] < -1.5, only 20% of the stars with...
In the context of the multi-messenger astronomy, the observation of an electromagnetic counterpart of the GW170817 event, known as kilonova (KN), provided evidence that the coalescence of binary neutron stars systems is a favourable stellar site hosting the rapid neutron capture process (r-process). Critical information related to the KN plasma composition can be derived through the analysis...
The rapid (r) and intermediate (i) neutron capture processes are critical for explaining the observed abundance patterns in stars. Both processes rely on neutron-capture rates, which remain largely unconstrained, experimentally.
For the i process, we report the first experimental constraint on the ¹³⁹Ba(n,γ)¹⁴⁰Ba reaction rate using radioactive ion beams (RIBs) from CARIBU at Argonne...
Recent large spectroscopic surveys have yielded significant new insights on heavy elements, their distribution in the Galaxy, and their evolution over time. However, these discoveries have also raised new questions that require investigation using even larger samples of stars, more precise abundance measurements, and data on key, yet challenging-to measure, elements.
Following an overview of...
Presolar grains are submicron- to micron-sized meteoritic grains that originate from stellar winds lost from the surfaces of multiple stars and from the ejecta produced by stellar explosions. Among the best-studied presolar phases is SiC. Multielement isotope analyses of presolar SiC grains indicate that most have origins in AGB stars and core-collapse Type II supernovae (CCSNe). AGB dust...
We present nucleosynthesis and light-curve calculations for a new site of the r-process from magnetar giant flares (GFs). Motivated by radio afterglow observations which indicate sizable baryon ejecta from GFs, Cehula et al. (2024) recently proposed a scenario whereby magnetar crustal material is ejected as a result of a shock driven into its surface layers during the reconnection-driven GF....
Metal-poor stars play a key role in understanding the nucleosynthesis of heavy elements in the early Universe, as their chemical abundances reflects the composition of the gas in which they formed.
High-resolution spectra show that metal-poor stars have robust chemical abundance patterns in the 60$<$Z$<$70 region, while variations are visible in region of the lighter heavy elements...
The Sagittarius (Sgr) dwarf galaxy experienced its first in-fall into the Milky Way (MW) about 5 Gyr ago. As it is being tidally stripped by the MW, its core and two stellar streams are now visible in the Sky, as well as various associated globular clusters. Given its proximity, it is an ideal test-bed for galactic chemo-dynamical models. So far, studies have typically focussed on metal-rich...
The reactions 13C(a,n)16O and 22Ne(a,n)25Mg are the neutron sources for the main and (the latter) the weak s process. Their cross sections need to be known at very low energies to provide for reliable astrophysical reaction rates in the s process energy windows. In the recent years there has been a world wide effort to both directly and indirectly measure these cross sections at low energies,...
This paper presents a general review of the Asymptotic Giant Branch
(AGB) evolutionary stages for Low and Intermediate Mass Stars and of the
nucleosynthesis processes occurring in them, chiefly as a consequence of the activation, in their final phases, of two crucial neutron-releasing reactions, 13 C(a,n) 16 O and 22 Ne(a,n) 25 Mg. These are jointly responsible for the production of most of...
The Galactic-Center (GC) region of the Milky Way has been a focal point for astronomers for many years, yet its formation history remains a subject of debate. So far, thanks to near-infrared spectroscopic observations, which suffer least from interstellar extinction, abundances of Fe-peak, alpha, and s-process elements have been determined for dozens of stars residing within the GC region....
The origin of heavy r-process elements in the universe is still a matter of great debate, with a confirmed scenario being neutron star (NS) mergers. Additional relevant sites could be specific classes of supernovae (SNe), such as Type Ib/c, where a central engine pushes neutron-rich material outwards, contributing to the ejecta of the massive exploding star. We investigate our ability to infer...
Abstract: Carbon-oxygen (C-O) shell interactions in the late evolutionary stages of massive stars play a crucial role in determining their final fate and have a significant impact on the pre-supernova and explosive nucleosynthesis. In this talk, I will explore the complex dynamics within C-O shells, and how these interactions drive the production of intermediate and heavy elements. Recent...
We present two recently developed ab initio methods for the calculation of beta decay spectra of light to heavy nuclei in astrophysical contexts.
The first method uses a variational approach with trial wave functions expanded in multidimensional Gaussian basis sets to accurately account for the electron-electron correlation in order to calculate bound and scattering states of few-body...
Globular clusters (GCs) are important stellar objects for understanding the formation and evolution of our Galaxy, providing crucial constraints to the chemical evolution and assembly history of the Galactic halo. Although there have been many individual efforts to characterise GCs in terms of heavy elements chemically, there is a lack of a global analysis with a homogeneous method. I present...
It is common opinion that AM CVn systems end their life as peculiar SNe Ia events due to detonation of a massive He layer piled up via mass transfer onto the CO WD component.
However, it has been shown that, if the effects of rotation are properly taken into account in modeling the evolution of the accretor in these systems, the accreting WD experiences recurrent very strong He-flashes during...
About half the elements heavier than iron in the Universe, like silver and gold, are created in the rapid neutron-capture (r-)process. However, today, almost 70 years after the theoretical prediction of this process, it is still highly debated in what type of stellar explosions it can take place. One of the best places to search for answers is in ancient, metal-poor stars formed from the...
Kilonovae are the transients powered by the radioactive decay of r-process elements, usually associated with neutron star mergers (NSMs). The late-time spectrum of NSMs is the most important tool to investigate the origin of the heaviest elements including the actinides, their nucleosynthesis at these sites, the environments of their production, and whether or not their abundances can be...
Cross-sections for neutron-induced interactions with molybdenum, in particular the neutron capture cross sections, play a significant role in various fields ranging from nuclear astrophysics to nuclear power plants and the development of innovative nuclear technologies. Molybdenum is found in pre-solar silicon carbide (SiC) grains and an accurate knowledge of its neutron capture cross section...
Propagating nuclear uncertainties to nucleosynthesis simulations is key to understand the impact of theoretical uncertainties on the predictions, especially for processes far from the stability region, where nuclear properties are scarcely known. While systematic (model) uncertainties have been thoroughly studied, the statistical (parameter) ones have been more rarely explored, as constraining...
The astrophysical i process has been proposed to explain astronomical observations that could not be explained by the traditional s and r processes. It involves nuclei that are a few steps from stability where the main missing piece of information from the nuclear physics side is neutron-capture reaction rates. In this talk I will present an experimental program that aims at constraining...
The nuclear mechanism responsible for roughly half of the heavy-elements (Z>30) abundances in our Solar system---the rapid neutron capture (r) process---was long thought to produce a "universal" abundance pattern. However, recent studies have challenged r-process universality by identifying significant variations between the elemental abundances patterns of metal-poor ([Fe/H]<-1.0),...
A realistic and detailed description of neutrinos in binary neutron star (BNS) mergers is essential to build reliable models of such systems. To this end, we present BNS_NURATES, a novel open-source numerical library designed for the efficient on-the-fly computation of neutrino interactions, with particular focus on regimes relevant to BNS mergers. BNS_NURATES targets a higher level of...
A linear relation between [s/alpha] and age has been found for stars with near solar metallicity. However, this "chemical clock" relationship has been shown to be non-universal, with dependencies on metallicity and position in the Galaxy. Using a novel empirical technique for recovering stellar birth radii (Rbirth) in observations, I will show the cosmic time evolution of [Ce/Mg], [Ba/Mg], and...
In high energy astrophysical processes involving compact objects, such as core-collapse supernovae or neutron star mergers, neutrinos are likely to play an important role in the synthesis of nuclides. Neutrinos in these environments can experience collective flavor oscillations driven by neutrino-neutrino coherent forward scattering. Recently, there has been interest in exploring potential...
The nucleosynthetic pathway of the rapid neutron capture process (r-process) proceeds far to the neutron-rich side of the valley of beta stability. Particularly for the heaviest species, this region of the nuclear chart lies well past where current rare isotope facilities have so far been able to reach. Thus simulations of the r-process rely on nuclear theory for key nuclear properties...
The reaction 22Ne(𝛼,𝛾)26Mg is associated with several questions in nuclear astrophysics, such as the Mg isotope ratio in stellar atmospheres and the nucleosynthesis of element beyond Fe through its competition with the neutron source 22Ne(𝛼,𝑛)25Mg.
Due to very low stellar energies and therefore very low cross section, direct experiments have been only able to provide upper limits below a...
The origin of the rapid neutron-capture (r-) process is a major question in astrophysics. The clue to answer this question is the chemical abundance patterns of extremely metal-poor (EMP) stars with [Fe/H] $< -3$, which are believed to reflect the nucleosynthesis yields of a single event. Recent high-resolution spectroscopic observations have shown that the abundance patterns of...
Binary neutron star (BNS) mergers eject neutron-rich matter, providing ideal conditions for the nucleosynthesis of heavy elements via the r-process. The radioactive decay of these elements powers a quasi-thermal electromagnetic transient known as kilonova (KN). Despite significant progress since the detection of GW170817, many open questions about KNe remain, such as the interpretation of the...
Low- and intermediate-mass (LIM) stars are fundamental to the Universe’s chemical evolution, yet their element production remains poorly understood. Recent observations of post-AGB stars reveal striking chemical diversity—some exhibit strong carbon and s-process enrichment, while others show no trace of these elements. Binary interactions further complicate this picture, with most post-AGB...
We provide an update on nucleosynthesis beyond strontium, utilizing the latest nuclear data for both the slow (s-process) and rapid (r-process) neutron capture processes. A significant portion of the r-process abundance distribution is associated with neutron star mergers (NSMs).
At the state of the art, precise observational constraints on their nucleosynthesis are not yet available, and...
Observational studies focusing on low- to intermediate-mass evolved stars, such as post-AGB stars, reveal remarkable diversity in their chemical compositions, particularly in terms of CNO abundance and s-process enrichment. These stars provide critical insights into AGB nucleosynthesis, dredge-up events, and hot-bottom burning. However, the mechanisms driving the observed diversity in their...
Kilonovae (KNe) are promising electromagnetic signals arising from compact binary mergers, which offer to nuclear astrophysicists a unique window to study the heavy-element nucleosynthesis driven by the rapid neutron capture (r-process) nucleosynthesis predicted to occur in this astrophysical environment. Deeply heterogeneous post-merging ejecta composition of both light and heavy-r process...
Barium (Ba) stars belong to binary systems where a former asymptotic giant branch (AGB, now a white dwarf) star polluted the less evolved companion, which became enriched with material produced through the slow neutron capture process (s process). The currently observed Ba star preserves the abundance pattern of the AGB, allowing us to test the imprints of the s process. Comparing different...
Kilonovae are optical-IR transients powered by radioactive decay of r-process elements produced in neutron star merger ejecta. The nature of r-process elements is imprinted in kilonova light curves and spectra. In this talk, I review kilonova light curve modelings, opacity of heavy elements, and nebular emission. In addition, I will talk about what we learned from the first neutron star...
Neutron-capture reactions drive the formation of elements heavier than iron, occurring through both the slow (s-) process in low-mass AGB and massive stars, and the rapid (r-) process in explosive stellar environments. Recently, the more exotic i-process, which involves higher neutron densities and more exotic nuclei than the s-process, is also gaining great interest.
For stable nuclei...
In recent years, the spectroscopic analysis of stars in Galactic open clusters showed a peculiar behavior regarding the slow neutron capture processes. On one hand, clusters at ages younger than 200 Myr display an unexpected over-abundance of Ba, reaching values up to ~0.7 dex at 30 Myr. On the other hand, regarding the other s-process elements such as Y, Zr, La and Ce, there is a general...
We run slow neutron-capture process (s process) nucleosynthesis calculations with the Monash post-processing code for seven stellar structure evolution models of low-mass asymptotic giant branch (AGB) stars with new sets of nuclear input. We present our new nucleosynthesis predictions of a selection of isotopic ratios and compare them to the corresponding ratios measured in presolar...
The LMS-1/Wukong stream represents the only chance locally to study a low-mass dwarf galaxy and globular cluster system. As a low mass dwarf galaxy, it also offers insight into the extreme chemical abundances and rare nucleosynthesis now synonymous with these objects. Currently on a polar orbit, just north of the Galactic Bulge, LMS-1 was likely a major contributor to the build up of the inner...
According to observations and numerical simulations, the Milky Way could exhibit several spiral arm modes with multiple pattern speeds,
wherein the slower patterns are located at larger Galactocentric
distances. Our aim is to quantify the effects of the spiral arms on
the azimuthal variations of the chemical abundances for oxygen, iron
and for the first time for neutron-capture elements...
The Milky Way is an environment rich with satellite galaxies, stellar streams and accreted systems. Looking at detailed chemical abundance patterns of individual stars in these systems allows us to trace back different nucleosynthetic sources, such as the slow (s), intermediate (i) and rapid (r) neutron-processes. Recent observations of these systems suggest that the i-process might have been...
The compilation1 of the beta-decay rates, based on the method developed in PART
I,2 has been extensively used for various s-process models. Given the advent of a
sophisticated modeling of the s-process associated with the thermal pulse/inter-pulse
and 3rd dredge-up phase in low-mass stars, and of a possibility of the s-processing
in the core/shell carbon burning phase in massive stars, it...
The abundances of neutron-capture elements in metal-poor stars are crucial for understanding the astrophysical sites and mechanisms responsible for heavy-element nucleosynthesis. While the very metal-poor regime ([Fe/H] < -2.5) has been extensively studied, the intermediate metallicity range (-2.5 \leq [Fe/H] \leq -1.5) remains poorly explored, leaving a significant gap in our understanding of...
Massive stars play a crucial role in the chemical evolution of galaxies, particularly enriching the interstellar medium with heavy elements. Recent stellar modelling studies have highlighted the beneficial effects of rotation in massive stars, enhancing their nucleosynthesis especially at low metallicies, where stars are expected to rotate faster. Indeed, once rotation is taken into account...
The field of chemical evolution of galaxies is key to understanding the origin and distribution of neutron-capture elements, able to provide insights into the astrophysical sites responsible for heavy-element nucleosynthesis, as well as the mechanisms that govern their dispersal throughout galaxies. In this review talk, I will present both past and recent advancements in this field. By...
S-process elements (Y, Zr, Ba, Ce), produced via slow neutron-capture processes in stars, are key tracers of stellar and Galactic evolution. When paired with alpha-elements (Mg, Ca, Si, Ti) in abundance ratios, they serve as chemical clocks, providing a powerful tool for estimating stellar ages. In this talk, I present a detailed spectroscopic analysis of 68 Kepler red giant stars, offering...
Neutron capture reactions are the main contributors to the synthesis of the heavy elements through the s-process. 22Ne(α, n)25Mg is the main neutron source in stars together with 13C(α, n)16O. In the relevant stellar energy (450 keV < Ecm < 750 keV) few data ara available, I.e. reaction cross section upper limits from direct experiments and highly uncertain estimates from indirect sources...
Several Carbon Enhanced Metal-Poor (CEMP) stars have been categorized as CEMP-rs, denoting that their spectra show overabundances both slow (s-) and rapid (r-) process elements. The nature of these stars is not yet explained, but hypotheses such as the “double pollution” and the intermediate (i-) process nucleosynthesis have been proposed. Two groups of authors have studied the stars GIU...
The rapid neutron capture (r-) process is responsible for producing half of the elements heavier than iron in the Universe. Significant uncertainties remain in understanding the astrophysical environments capable of generating the necessary intense neutron fluxes. Detailed hydrodynamical simulations of proposed astrophysical scenarios (e.g. binary neutron star mergers, magneto-hydrodynamical...
The abundances in the Solar System are the result of the contributions from many generations of stars. Beyond the Fe-group elements, about half of the abundances were made by the slow neutron-capture process, or s-process. Stars with initial mass of the order of 9 solar masses or larger contributed a relevant fraction of the s-process elements between Fe (Z=26) and Zr (Z=40), with free...
Presolar grains condensed around ancient dying stars that contributed dust from which our Solar System was made. Discovered in the 1980’s, these sub-micron to tens of microns-sized pieces of dust are identified on the basis of their highly anomalous isotopic compositions, compared to that of objects that formed in the Solar System. The isotopic analysis of presolar grains in the laboratory...
Contrary to the traditional view of globular clusters as single stellar populations, some ancient star clusters exhibit remarkable diversity in their neutron capture process element abundances. The Galactic Archaeology with HERMES (GALAH) Survey provides detailed measurements of key neutron capture process elements, including Sr, Y, Zr, Mo, Ru, Ba, La, Ce, Nd, Sm, and Eu. Recent observational...
A Type Ia supernova (SNIa) marks the catastrophic explosion of a white dwarf in a binary system. These events play a crucial role in galactic chemical evolution and serve as pivotal standardizable candles for measuring cosmic distances, underpinning the discovery of the Universe's accelerated expansion. However, the progenitors of SNIa remain uncertain, introducing challenges to their use in...
Among the chemically peculiar metal-poor stars, the two sub-classes of carbon-enhanced metal-poor (CEMP) stars, the so called CEMP-s and CEMP-r/s stars are powerful tracers of slow (s) and intermediate (i) neutron-capture nucleosynthesis, evolution of binary systems and mechanisms of mass-transfer. The epoch of the earliest s-process nucleosynthesis that influenced the chemical enrichment, as...
The nucleosynthetic s-process occurring in AGB stars from ∼ 1−6M⊙ is responsible for creating half of the heavy elements in the universe, the chemical imprint of which can be studied by observing the material on the surface of binary barium (Ba), CH, and carbon-enhanced metal-poor (CEMP) stars. We simulate the results of AGB mass transfer in binaries by computing a grid of binary stellar...
Aim. We determine r- to s-process contributions to Ba isotope mixture along with Ba, Eu, and Sr NLTE abundances in a sample of very metal-poor (VMP) stars. The selected stars have [Ba/H] < -2.2 and, thus, formed before the contribution from the main s-process in low and intermediate stars became significant. Some of our sample stars are enhanced in Sr with [Sr/Ba] up to 0.7. These stars gained...
Core-collapse supernovae are one of the most important sources of heavy elements
in the universe. Therefore, accurate modeling of the stellar evolution and the explosion
phases are crucial to obtain accurate predictions of their nucleosynthetic
signature. In this talk I will present results from nucleosynthesis calculations of realistic
neutrino-driven supernova explosions in spherical...
The isotopic compositions of Sr, Zr, Mo, Ru, and Ba in presolar SiC and graphite have much to tell us about nucleosynthesis in stars. We highlight here two examples from recent simultaneous measurements on multiple elements in single presolar grains. (1) From their Mo and Ru isotopic compositions, the mainstream, Y-, and Z-type SiC grains have remarkably constant and solar-like ratios of r-...
