Showing papers on "Stellar nucleosynthesis published in 2010"

Quantifying the uncertainties of chemical evolution studies II. Stellar yields

Abstract: Context. Galactic chemical evolution models are useful tools for interpreting the large body of high-quality observational data on the chemical composition of stars and gas in galaxies that have become available in recent years. Aims. This is the second paper of a series that aims at quantifying the uncertainties in chemical evolution model predictions related to the underlying model assumptions. Specifically, it deals with the uncertainties due to the choice of the stellar yields. Methods. We adopted a widely used model for the chemical evolution of the Galaxy to test the effects of changing the stellar nucleosynthesis prescriptions on the predicted evolution of several chemical species. Up-to-date results from stellar evolutionary models were carefully taken into account. Results. We find that, except for a handful of elements whose nucleosynthesis in stars is well understood by now, large uncertainties still affect model predictions. This is especially true for the majority of the iron-peak elements, but also for much more abundant species such as carbon and nitrogen. The main causes of the mismatch we find among the outputs of different models assuming different stellar yields and among model predictions and observations are (i) the adopted location of the mass cut in models of type II supernova explosions; (ii) the adopted strength and extent of hot bottom burning in models of asymptotic giant branch stars; (iii) the neglection of the effects of rotation on the chemical composition of the stellar surfaces; (iv) the adopted rates of mass loss and of (v) nuclear reactions; and (vi) the different treatments of convection. Conclusions. Our results suggest that it is mandatory to include processes such as hot bottom burning in intermediate-mass stars and rotation in stars of all masses in accurate studies of stellar evolution and nucleosynthesis. In spite of their importance, both these processes still have to be better understood and characterized. As for massive stars, presupernova models computed with mass loss and rotation are available in the literature, but they still wait for a self-consistent coupling with the results of explosive nucleosynthesis computations.

Evolution and nucleosynthesis of extremely metal-poor and metal-free low- and intermediate-mass stars - II. s-process nucleosynthesis during the core He flash

Abstract: Context. Models of primordial and hyper-metal-poor stars that have masses similar to the Sun are known to experience an ingestion of protons into the hot core during the core helium flash phase at the end of their red giant branch evolution. This produces a concurrent secondary flash powered by hydrogen burning that gives rise to further nucleosynthesis in the core.Aims. We aim to model the nucleosynthesis occurring during the proton ingestion event to ascertain if any significant neutron-capture nucleosynthesis occurs.Methods. We perform post-process nucleosynthesis calculations on a one-dimensional stellar evolution calculation of a star with mass 1 M ⊙ and a metallicity of [ Fe/H ] = − 6.5 that suffers a proton ingestion episode. Our network includes 320 nuclear species and 2366 reactions and treats mixing and burning simultaneously.Results. We find that the mixing and burning of protons into the hot convective core leads to the production of 13 C, which then burns via the 13 C(α , n )16 O reaction, releasing a large number of free neutrons. During the first two years of neutron production the neutron poison 14 N abundance is low, allowing the prodigious production of heavy elements such as strontium, barium, and lead via slow neutron captures (the s process). These nucleosynthetic products are later carried to the stellar surface and ejected via stellar winds. We compare our results with observations of the hyper-metal-poor halo star HE 1327-2326, which shows a strong Sr overabundance. Conclusions. Our model provides the possibility of self-consistently explaining the Sr overabundance in HE 1327-2326 together with its C, N, and O overabundances (all within a factor of ~4) if the material were heavily diluted, for example, via mass transfer in a wide binary system. The model produces at least 18 times too much Ba than observed, but this may be within the large modelling uncertainties. In this scenario, binary systems of low mass must have formed in the early Universe. If this is true, it puts constraints on the primordial initial mass function.

Big-Bang nucleosynthesis with updated nuclear data

Abstract: Primordial nucleosynthesis is one of the three evidences for the Big-Bang model together with the expansion of the Universe and the Cosmic Microwave Background. There is a good global agreement over a range of nine orders of magnitude between abundances of 4He, D, 3He and 7Li deduced from observations and calculated primordial nucleosynthesis. This comparison was used to determine the baryonic density of the Universe. For this purpose, it is now superseded by the analysis of the Cosmic Microwave Background (CMB) radiation anisotropies. Big-Bang nucleosynthesis remains, nevertheless, a valuable tool to probe the physics of the early Universe. However, the yet unexplained, discrepancy between the calculated and observed lithium primordial abundances, has not been reduced, neither by recent nuclear physics experiments, nor by new observations.

Effects of the variation of fundamental constants on Population III stellar evolution

Abstract: Aims. A variation of the fundamental constants is expected to affect the thermonuclear rates important for stellar nucleosynthesis. In particular, because of the very low resonant energies of 8 Be and 12 C, the triple α process is extremely sensitive to any such variations.Methods. Using a microscopic model for these nuclei, we derive the sensitivity of the Hoyle state to the nucleon-nucleon potential, thereby allowing for a change in the magnitude of the nuclear interaction. We follow the evolution of 15 and 60 zero-metallicity stellar models, up to the end of core helium burning. These stars are assumed to be representative of the first, Population III stars.Results. We derive limits on the variation in the magnitude of the nuclear interaction and model dependent limits on the variation of the fine structure constant based on the calculated oxygen and carbon abundances resulting from helium burning. The requirement that some 12 C and 16 O be present at the end of the helium burning phase allows for permille limits on the change in the nuclear interaction and limits of the order of 10-5 on the fine structure constant relevant at a cosmological redshift of z ~ 15-20.

Quantifying the uncertainties of chemical evolution studies. II. Stellar yields

Abstract: This is the second paper of a series which aims at quantifying the uncertainties in chemical evolution model predictions related to the underlying model assumptions. Specifically, it deals with the uncertainties due to the choice of the stellar yields. We adopt a widely used model for the chemical evolution of the Galaxy and test the effects of changing the stellar nucleosynthesis prescriptions on the predicted evolution of several chemical species. We find that, except for a handful of elements whose nucleosynthesis in stars is well understood by now, large uncertainties still affect the model predictions. This is especially true for the majority of the iron-peak elements, but also for much more abundant species such as carbon and nitrogen. The main causes of the mismatch we find among the outputs of different models assuming different stellar yields and among model predictions and observations are: (i) the adopted location of the mass cut in models of type II supernova explosions; (ii) the adopted strength and extent of hot bottom burning in models of asymptotic giant branch stars; (iii) the neglection of the effects of rotation on the chemical composition of the stellar surfaces; (iv) the adopted rates of mass loss and of (v) nuclear reactions, and (vi) the different treatments of convection. Our results suggest that it is mandatory to include processes such as hot bottom burning in intermediate-mass stars and rotation in stars of all masses in accurate studies of stellar evolution and nucleosynthesis. In spite of their importance, both these processes still have to be better understood and characterized. As for massive stars, presupernova models computed with mass loss and rotation are available in the literature, but they still wait for a self-consistent coupling with the results of explosive nucleosynthesis computations.

The Zr-92(n,gamma) reaction and its implications for stellar nucleosynthesis

Abstract: Because the relatively small neutron capture cross sections of the zirconium isotopes are difficult to measure, the results of previous measurements are often not adequate for a number of problems in astrophysics and nuclear technology. Therefore, the Zr-92(n,gamma) cross section has been remeasured at the CERN n_TOF facility, providing a set of improved parameters for 44 resonances in the neutron energy range up to 40 keV. With this information the cross-section uncertainties in the keV region could be reduced to 5% as required for s-process nucleosynthesis studies and technological applications.

Galactic astroarchaeology: reconstructing the bulge history by means of the newest data

Abstract: The chemical abundances measured in stars of the Galactic bulge offer an unique opportunity to test galaxy formation models as well as impose strong constraints on the history of star formation and stellar nucleosynthesis. The aims of this paper are to compare abundance predictions from a detailed chemical evolution model for the bulge with the newest data. Some of the predictions have already appeared on previous paper (O, Mg, Si, S and Ca) but some other predictions are new (Ba, Cr and Ti). We compute several chemical evolution models by adopting different initial mass functions for the Galactic bulge and then compare the results to new data including both giants and dwarf stars in the bulge. In this way we can impose strong constraints on the star formation history of the bulge. We find that in order to reproduce at best the metallicity distribution function one should assume a flat IMF for the bulge not steeper than the Salpeter one. The initial mass function derived for the solar vicinity provides instead a very poor fit to the data. The [el/Fe] vs. [Fe/H] relations in the bulge are well reproduced by a very intense star formation rate and a flat IMF as in the case of the stellar metallicity distribution. Our model predicts that the bulge formed very quickly with the majority of stars formed inside the first 0.5 Gyr. Our results strongly suggest that the new data, and in particular the MDF of the bulge, confirm what concluded before and in particular that the bulge formed very fast, from gas shed by the halo, and that the initial mass function was flatter than in the solar vicinity and in the disk, although not so flat as previously thought. Finally, our model can also reproduce the decrease of the [O/Mg] ratio for [Mg/H] > 0 in the bulge, which is confirmed by the new data and interpreted as due to mass loss in massive stars.

Primordial Nucleosynthesis: The Predicted and Observed Abundances and Their Consequences

Abstract: For a brief time in its early evolution the Universe was a cosmic nuclear reactor. The expansion and cooling of the Universe limited this epoch to the first few minutes, allowing time for the synthesis in astrophysically interesting abundances of only the lightest nuclides (D, 3He, 4He, 7Li). For big bang nucleosynthesis (BBN) in the standard models of cosmology and particle physics (SBBN), the SBBN-predicted abundances depend on only one adjustable parameter, the baryon density parameter (the ratio by number of baryons (nucleons) to photons). The predicted and observed abundances of the relic light elements are reviewed, testing the internal consistency of primordial nucleosynthesis. The consistency of BBN is also explored by comparing the values of the cosmological parameters inferred from primordial nucleosynthesis for the standard model and for models with non-standard early Universe expansion rates with those determined from studies of the cosmic background radiation, which provides a snapshot of the Universe some 400 thousand years after BBN ended.

Cosmochemistry : the melting pot of the elements : XIII Canary Islands Winter School of Astrophysics, Puerto de la Cruz, Tenerife, Spain, November 19-30, 2001

Abstract: 1 Primordial alchemy: from the Big Bang to the present Universe G Steigman 2 Stellar nucleosynthesis N Langer 3 Obervational aspects of stellar nucleosynthesis D L Lambert 4 Abundance determinations in HII regions and planetary nebulae G Stasinska 5 Element abundances in nearby galaxies D R Garnett 6 Chemical evolution of galaxies and intracluster medium FMatteucci 7 Element abundances through the cosmic ages M Pettini

A holistic abundance analysis of r-rich stars

Abstract: The chemical abundances of metal-poor stars are an excellent test bed by which to set new constraints on models of neutron-capture processes at low metallicity. Some r-process-rich (hereafter r-rich) metal-poor stars, such as HD 221170, show an overabundance of the heavier neutron-capture elements and excesses of lighter neutron-capture elements. The study of these r-rich stars could give us a better understanding of weak and main r-process nucleosynthesis at low metallicity. Based on conclusions from the observation of metal-poor stars and neutron-capture element nucleosynthesis theory, we set up a model to determine the relative contributions from weak and main r-processes to the heavy-element abundances in metal-poor stars. Using this model, we find that the abundance patterns of light elements for most sample stars are close to the pattern of weak r-process stars, and those of heavier neutron-capture elements very similar to the pattern of main r-process stars, while the lighter neutron-capture elements can be fitted by the mixing of weak and main r-process material. The production of weak r-process elements appears to be associated with the light elements, while the production of main r-process elements is almost decoupled from that of the light elements. We compare our results with the observed data at low metallicities, showing that the predicted trends are in good agreement with the observed trends, at least for the metallicity range [Fe/H] < -2.1. For most sample stars, the abundance patterns of both neutron-capture elements and light elements could be best explained by a star formed in a molecular cloud that has been polluted by both weak and main r-process material.

Multiple main sequence of globular clusters as a result of inhomogeneous big bang nucleosynthesis

Abstract: A new mechanism for enhancing the helium abundance in the blue main sequence stars of $\ensuremath{\omega}$ Centauri and NGC 2808 is investigated. We suggest that helium enhancement was caused by the inhomogeneous big bang nucleosynthesis. Regions with extremely high baryon-to-photon ratios are assumed to be caused by the baryogenesis. Its mass scale is also assumed to be ${10}^{6}{M}_{\ensuremath{\bigodot}}$. An example of the mechanisms to realize these two things was already proposed as the Affleck-Dine baryogenesis. As the baryon-to-photon ratio becomes larger, the primordial helium abundance is enhanced. We calculated the big bang nucleosynthesis and found that there exists a parameter region yielding enough helium to account for the split of the main sequence in the aforementioned globular clusters while keeping the abundance of other elements compatible with observations. Our mechanism predicts that heavy elements with the mass number of around 100 is enhanced in the blue main sequence stars. We estimate the time scales of diffusion of the enhanced helium and mass accretion in several stages after the nucleosynthesis to investigate whether these processes diminish the enhancement of helium. We found that the diffusion does not influence the helium content. A cloud with a sufficiently large baryon-to-photon ratio to account for the multiple main sequence collapsed immediately after the recombination. Subsequently, the cloud accreted the ambient matter with the normal helium content. If the star formation occurred both in the collapsed core and the accreted envelope, then the resultant star cluster has a double main sequence.

The Evolution of Elements and Isotopes

Abstract: The basic building blocks of all minerals are the approximately 290 stable or long-lived isotopes of 84 elements. Yet, when the universe began and nuclear reactions ceased after about 15 minutes, the only elements present were hydrogen, helium, and traces of lithium. After the groundbreaking work by Cameron and Burbidge and coworkers in the 1950s, it is now understood that all the other elements are made in stars in an ongoing cycle of nucleosynthesis. Stars form, create new elements via nuclear reactions, and finally disperse the new elements into space via winds and explosions, forming the seeds for new stars.

Effects of the variation of fundamental constants on Pop III stellar evolution

Abstract: Aims. A variation of the fundamental constants is expected to affect the thermonuclear rates important for stellar nucleosynthesis. In particular, because of the very low resonant energies of 8 Be and 12 C, the triple α process is extremely sensitive to any such variations. Methods. Using a microscopic model for these nuclei, we derive the sensitivity of the Hoyle state to the nucleon-nucleon potential,

Helium in stellar atmospheres

Abstract: Helium, which was first discovered on the sun with the help of spectral analysis, plays, together with hydrogen, a principal role in astrophysics. We consider here two fundamental quantities: primordial helium abundance formed during Big Bang nucleosynthesis and the current initial helium abundances in nearby stars. It is shown that stellar atmospheres are enriched in helium during the main-sequence stage. Observational evidence for helium contamination in close OB-binaries is discussed. Stars with strong abundance anomalies are considered, such as chemically peculiar Ap and Bp helium-deficient stars and some types of objects with helium atmospheres.

Observational Constraint on Heavy Element Production in Inhomogeneous Big Bang Nucleosynthesis

Abstract: Based on a scenario of the inhomogeneous big-bang nucleosynthesis (IBBN), we investigate the detailed nucleosynthesis that includes the production of heavy elements beyond 7 Li. From the observational constraints on light elements of 4 He and D for the baryon-to-photon ratio given by WMAP, possible regions found on the plane of the volume fraction of the high density region against the ratio between high- and low-density regions. In these allowed regions, we have confirmed that the heavy elements beyond Fe can be produced appreciably, where p- and/or r-process elements are produced well simultaneously compared to the solar system abundances. We suggest that recent observational signals such as 4 He overabundance in globular clusters and high metallicity abundances in quasars could be partly due to the results of IBBN. Possible implications are given for the formation of the first generation stars.

ISOLTRAP results 2006–2009

Abstract: Since 2006 the ISOLTRAP mass spectrometer has provided high-precision masses of many short-lived nuclides located all across the nuclear chart with half-lives down to a few 10 ms. These nuclides range from the two-proton halo candidate 17Ne, via the neutron-rich magic 80Zn and 132Sn, up to 229Rn which was identified for the first time. The results show that ISOLTRAP is a versatile tool well suited to address physics topics such as nuclear structure, stellar nucleosynthesis, or the weak interaction.

Li isotopes in metal-poor halo dwarfs, a more and more complicated story

Abstract: The nuclei of the lithium isotopes are fragile, easily destroyed, so that, at variance with most of the other elements, they cannot be formed in stars through steady hydrostatic nucleosynthesis. The 7Li isotope is synthesized during primordial nucleosynthesis in the first minutes after the Big Bang and later by cosmic rays, by novae and in pulsations of AGB stars (possibly also by the "nu" process). 6Li is mainly formed by cosmic rays. The oldest (most metal-deficient) warm galactic stars should retain the signature of these processes if, (as it had been often expected) lithium is not depleted in these stars. The existence of a "plateau" of the abundance of 7Li (and of its slope) in the warm metal-poor stars is discussed. At very low metallicity ([Fe/H]<-2.7 dex the star to star scatter increases significantly towards low Li abundances. The highest value of the lithium abundance in the early stellar matter of the Galaxy (A(7Li) = 2.2 dex) is much lower than the the value A(7Li) = 2.72 predicted by the standard Big Bang nucleosynthesis, according to the specifications found by the satellite WMAP. After gathering a homogeneous stellar sample, and analysing its behaviour, possible explanations of the disagreement between Big Bang and stellar abundances are discussed (including early astration and diffusion). On the other hand, possibilities of lower productions of 7Li in the standard and/or non-standard Big Bang nucleosyntheses are briefly evoked. A surprisingly high value (A(6Li)=0.8 dex) of the abundance of the 6Li isotope has been found in a few warm metal-poor stars. Such a high abundance of 6Li independent of the mean metallicity in the early Galaxy cannot be easily explained. But are we really observing 6Li ?

The Evolution of Massive Stars and the Concomitant Non-explosive and Explosive Nucleosynthesis

Abstract: These lectures are concerned with some aspects of the evolution of massive stars and of the concomitant nucleosynthesis. They complement other lectures in this volume. Special emphasis is put on the production of the nuclides heavier than iron by the r- and p-processes.

Explosive nucleosynthesis in massive stars

Abstract: In this short paper we will review the basic properties of the explosive nucleosynthesis in massive stars. In particular we will describe how the the basic properties of an expanding adiabatic shock wave, coupled to the behavior of the matter at various high temperatures to the presupernova evolution of a massive star, contribute to produce its final explosive yields. We also address the problem of the amount of mass which falls back onto the compact remnant, which depends not only on the hydrodinamical properties of the explosion but also on the properties of the presupernova star.

The Impact of Nucleosynthesis Models on Models of the Chemical Evolution of Disk Galaxies

Abstract: The impact of uncertainties in the relative efficiency of nucleosynthesis of various elements in stars on models of the chemical evolution of disk galaxies is studied using a single-zone model for the galactic evolution. The dependences of the abundances of 12C, 14N, 16O, and 56Fe on nucleosynthesis models are compared. The influence of the uncertainty in iron production by Type Ia supernovae on its abundance in a galaxy is also considered. It is concluded that differences in nucleosynthesis models can appreciably affect the results of modeling the early stages of galactic evolution, but this influence becomes insignificant at ages t> 109 yr. Uncertainties in the amount of iron ejected by Type Ia supernovae do not significantly influence the total galactic abundance of iron.

The Main Path to C, N, O Elements in Big Bang Nucleosynthesis

Abstract: The production of C, N, O elements in a standard big bang nucleosynthesis scenario is investigated. Using the up-to-date data of nuclear reactions in BBN, in particular the 8Li (n,γ) 9Li which has been measured in China Institute of Atomic Energy, a full nucleosynthesis network calculation of BBN is carried out. Our calculation results show that the abundance of 12C is increased for an order of magnitude after addition of the reaction chain 8Li(n,γ) 9Li(α,n) 12B(β) 12C, which was neglected in previous studies. We find that this sequence provides the main channel to convert the light elements into C, N, O in standard BBN.

Explosive nucleosynthesis in core-collapse supernovae

Abstract: The specific mechanism and astrophysical site for the production of half of the elements heavier than iron via rapid neutron capture (r-process) remains to be found. In order to reproduce the abundances of the solar system and of the old halo stars, at least two components are required: the heavy r-process nuclei (A>130) and the weak r-process which correspond to the lighter heavy nuclei (A<130). In this work, we present nucleosynthesis studies based on trajectories of hydrodynamical simulations for core-collapse supernovae and their subsequent neutrino-driven winds. We show that the weak r-process elements can be produced in neutrino-driven winds and we relate their abundances to the neutrino emission from the nascent neutron star. Based on the latest hydrodynamical simulations, heavy r-process elements cannot be synthesized in the neutrino-driven winds. However, by artificially increasing the wind entropy, elements up to A=195 can be made. In this way one can mimic the general behavior of an ejecta where the r-process occurs. We use this to study the impact of the nuclear physics input (nuclear masses, neutron capture cross sections, and beta-delayed neutron emission) and of the long-time dynamical evolution on the final abundances.

Development of a new bremsstrahlung source for nuclear astrophysics

Abstract: Nuclear reaction rate for photodisintegration and their inverse, charged particle and neutron capture reactions, are important input quantities for stellar nucleosynthesis In order to evaluate reaction rates precisely, both nuclear experiment and model prediction are needed Recently, real photon‐beam is used as powerful tools for astrophysics In this work, current status of the development of a new bremsstrahlung γ‐ray source with the electron linear accelerator at Hokkaido University will be presented

Presolar grains: a record of stellar nucleosynthesis and processes in interstellar space

Abstract: Overview Presolar grains give us a direct window into stellar nucleosynthesis and provide probes of processes in interstellar space and in the solar nebula. Known types of presolar grains originated in the winds or ejecta of stars that lived and died before the solar system formed. After presenting a short history of how presolar grains came to be recognized, we describe how to identify presolar grains, the techniques used to study them, and the various types of grains currently available for study. We then review what presolar grains can tell us about stellar nucleosynthesis, the environments around evolved stars and in the interstellar medium, and how they can be used as probes of conditions in the early solar system. Grains that predate the solar system In recent years, a new source of information about stellar nucleosynthesis and the history of the elements between their ejection from stars and their incorporation into the solar system has become available. This source is the tiny dust grains that condensed from gas ejected from stars at the end of their lives and that survived unaltered to be incorporated into solar system materials. These presolar grains (Fig. 5.1) originated before the solar system formed and were part of the raw materials for the Sun, the planets, and other solar-system objects. They survived the collapse of the Sun's parent molecular cloud and the formation of the accretion disk and were incorporated essentially unchanged into the parent bodies of the chondritic meteorites.

Chemical analysis of globular star clusters: theory and observation

Abstract: A few minutes after the Big Bang that created our Universe, nucleosynthesis reactions forged some lighter isotopes, including 7Li Ever since then, such reactions have taken place in the hot stellar interiors, providing the stars with the energy to shine and forming all chemical elements necessary for life as we know it In this thesis I describe how we have inferred the chemical composition of stars in a globular cluster, hosting one of the oldest stellar populations in our Galaxy, in order to address two fundamental astrophysical problems The first problem is related to lithium, and the prediction of its primordial abundance from present cosmological theories of how the Universe was born The Li abundances that we measure in the envelopes of globular cluster stars are lower than this estimate and we investigate the possibility that Li has been drained from the stellar surfaces This thesis presents observational evidence that low-mass stars experience a small increase in their surface Li abundances during the course of their late phases of evolution, supporting this hypothesis The second question is related to the formation and evolution of globular clusters It appears that these dense stellar environments early underwent a unique form of self- enrichment, by retaining the gas outflow from slow stellar winds The material was then incorporated into a second stellar generation with identical chemical signatures to the first, except for a handful of lighter elements, including sodium I here discuss several aspects of this stellar pollution process Only with a correct physical description of the radiative and convective energy transport through the stellar atmosphere, and the equilibrium state of the atoms, ions and molecules that form the tenuous gas, can we make solid predictions of the emergent spectrum and derive accurate abundances In particular, I discuss how the simplifying assumption of local thermal equilibrium give rise to systematic errors in the analysis of Li and Na spectral lines, commonly mis-estimating the elemental abundances in stars by 10–50%, and in certain cases considerably more Moreover, we have for the first time investigated the combined influence from departures from local thermal equilibrium and hydro-static equilibrium in the determination of the solar Na abundance

Primordial and Stellar Nucleosynthesis Chemical Evolution of Galaxies

Abstract: Following a brief introduction to early Universe cosmology, we present in some detail the results of primordial nucleosynthesis. Then we summarize the basic theory of nuclear reactions in stars and sketch the general rules of stellar evolution. We shortly review the subject of supernova explosions both by core collapse in massive stars (Type II) and carbon‐deflagration in binary systems when one of the components is a White Dwarf accreting mass from the companion (Type Ia). We conclude the part dedicated to nucleosynthesis with elementary notions on the s‐ and r‐process. Finally, we shortly address the topic of galactic chemical evolution and highlight some simple solutions aimed at understanding the main observational data on abundances and abundance ratios.

Nucleosynthesis: a field with still many open nuclear physics questions

Abstract: Stellar nucleosynthesis is a vastly interdisciplinary field. There is a large number of different problems invoked calling for a variety of different and complementary research fields. Impressive progress has been made for the last decades in the various fields related to nucleosynthesis, especially in experimental and theoretical nuclear physics, as well as in ground‐based or space astronomical observations and astrophysical modellings. In spite of that success, major problems and puzzles remain. The three major nucleosynthesis processes called for to explain the origin of the elements heavier than iron are described and the major pending questions discussed. As far as nuclear physics is concerned, good quality nuclear data is known to be a necessary condition for a reliable modelling of stellar nucleosynthesis. Through some specific examples, the need for further theoretical or experimental developments is also critically discussed in view of their impact on nucleosynthesis predictions.