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This contribution presents an extension of our r-process parameter study within the high-entropy-wind (HEW) scenario of corecollapse supernovae (ccSNe). One of the primary aims of this study was to obtain indications for the production of classical p-, s- and r-isotopes of the light trans-Fe elements in the Solar System (S.S.). Here, we focus on the nucleosynthesis origin of the anomalous isotopic compositions of Zr, Mo and Ru in presolar SiC X-grains (SNe grains). In contrast to the interpretation of other groups, we show that these grains do not represent the signatures of a ‘clean’ stellar scenario, but rather, are mixtures of an exotic nucleosynthesis component and S.S. material. We further confirm the results of our earlier studies whereby sizeable amounts of all stable p-, s- and r-isotopes of Zr, Mo and Ru can be co-produced by moderately neutron-rich ejecta of the low-entropy, charged-particle scenario of ccSNe (type II). The synthesis of these isotopes through a ‘primary’ production mode provides further means to revise the abundance estimates of the light trans-Fe elements from so far favoured ‘secondary’ scenarios like Type Ia SNe or neutron-bursts in exploding massive stars.

This article addresses three of the four nucleosynthesis processes involved in producing heavy nuclei beyond Fe (with a main focus on the r -process). Opposite to the fourth process (the s -process), which operates in stellar evolution during He- and C-burning, they are all related to explosive burning phases, (presumably) linked to core collapse supernova events of massive stars. The (classical) p -process is identified with explosive Ne/O-burning in outer zones of the progenitor star. It is initiated by the passage of the supernova shock wave and acts via photodisintegration reactions like a spallation process which produces neighboring (proton-rich) isotopes from pre-existing heavy nuclei. The reproduction of some of the so-called lighter p -isotopes with A 100 faces problems in this environment. The only recently discovered ν p -process is related to the innermost ejecta, the neutrino wind expelled from the hot proto-neutron star after core collapse and the supernova explosion. This neutrino wind is proton-rich in its early phase, producing nuclei up to 64Ge. Reactions with neutrinos permit to overcome decay/reaction bottlenecks for the flow beyond 64Ge, thus producing light p -isotopes, which face problems in the classical p -process scenario. The understanding of the r -process, being identified for a long time with rapid neutron captures and passing through nuclei far from stability, is still experiencing major problems. These are on the one hand related to nuclear uncertainties far from stability (masses, half-lives, fission barriers), affecting the process speed and abundance peaks. On the other hand the site is still not definitely located, yet. (i) Later, possibly neutron-rich, high entropy phases of the neutrino wind (if they materialize!) could permit its operation. (ii) Other options include the ejection of very neutron-rich neutron star-like matter, occurring possibly in neutron star mergers or core collapse supernova events with jets, related to prior stellar evolution with high rotation rates and magnetic fields. Two different environments are required for a weak and a main/strong r -process, witnessed by observations of low metallicity stars and meteoritic inclusions, which could possibly be identified with the two options listed above, i.e. the weak r -process could be related to the neutrino wind when changing from p -rich to n -rich conditions.

The astrophysical site of the r-process is still uncertain, and a full exploration of the systematics of this process in terms of its dependence on nuclear properties from stability to the neutron drip-line within realistic stellar environments has still to be undertaken. Sufficiently high neutron to seed ratios can only be obtained either in very neutron-rich low-entropy environments or moderately neutron-rich high-entropy environments, related to neutron star mergers (or jets of neutron star matter) and the high-entropy wind of core-collapse supernova explosions. As chemical evolution models seem to disfavor neutron star mergers, we focus here on high-entropy environments characterized by entropy $S$, electron abundance $Y_e$ and expansion velocity $V_{exp}$. We investigate the termination point of charged-particle reactions, and we define a maximum entropy $S_{final}$ for a given $V_{exp}$ and $Y_e$, beyond which the seed production of heavy elements fails due to the very small matter density. We then investigate whether an r-process subsequent to the charged-particle freeze-out can in principle be understood on the basis of the classical approach, which assumes a chemical equilibrium between neutron captures and photodisintegrations, possibly followed by a $\beta$-flow equilibrium. In particular, we illustrate how long such a chemical equilibrium approximation holds, how the freeze-out from such conditions affects the abundance pattern, and which role the late capture of neutrons originating from $\beta$-delayed neutron emission can play., Comment: 52 pages, 31 figures

We have performed large-scale nucleosynthesis calculations within the high-entropy-wind (HEW) scenario of type II supernovae. The primary aim was to constrain the conditions for the production of the classical "p-only" isotopes of the light trans-Fe elements. We find, however, that for electron fractions in the range 0.458 $\le$ Y$_e$ $\le$ 0.478, sizeable abundances of p-, s- and r-process nuclei between $^{64}$Zn and $^{98}$Ru are coproduced in the HEW at low entropies (S $\le$ 100) by a primary charged-particle process after an $\alpha$-rich freezeout. With the above Y$_e$ -- S correlation, most of the predicted isotopic abundance ratios within a given element (e.g. $^{64}$Zn(p)/$^{70}$Zn(r) or $^{92}$Mo(p)/$^{94}$Mo(p)), as well as of neighboring elements (e.g. $^{70}$Ge(s+p)/$^{74}$Se(p) or $^{74}$Se(p)/$^{78}$Kr(p)) agree with the observed Solar-System ratios. Taking the Mo isotopic chain as a particularly challenging example, we show that our HEW model can account for the production of all 7 stable isotopes, from "p-only" $^{92}$Mo, via "s-only" $^{96}$Mo up to "r-only" $^{100}$Mo. Furthermore, our model is able to reproduce the isotopic composition of Mo in presolar SiC X-grains.}, Comment: 10 pages, 2 figures

The exact conditions for the supernova high-entropy wind (HEW) as one of the favored sites for the rapid neutron-capture (r-) process still cannot be reproduced selfconsistently in present hydrodynamic simulations. Therefore, we have performed large-scale network calculations within a parameterized HEW model to constrain the necessary conditions for a full r-process, and to compare our results with recent astronomical observations. A superposition of entropy trajectories with model-inherent weightings results in an excellent reproduction of the overall solar-system isotopic abundances ( N r ,⊙ ) of the “main” r-process elements beyond Sn. For the lighter r-elements, our model supports earlier qualitative ideas about a multiplicity of nucleosynthesis processes in the Fe-group region. In the high-entropy-wind scenario, these suggestions are quantified, and the origin of the “missing” abundances to N r ,⊙ is determined to be a rapid primary charged-particle (α-) process, thus excluding a classical “weak” neutron-capture component. This explains the recent halo-star observations of a non-correlation of Cu–Ge and Sr–Zr with metallicity [Fe/H] and r-process enrichment [Eu/H]. Moreover, for the first time a partial correlation with the “main” r-process is identified for Ru and Pd.

Nucleosynthesis theory predicts that half of the chemical elements above Fe are formed in explosive stellar scenarios by the r-process. A correct modelling of this process requires knowledge of nuclear properties very far from stability and a detailed description of the astrophysical environments. Using updated experimental and theoretical nuclear-physics data, we have performed detailed r-process calculations within the classical, site-independent “waiting-point” approximation and the “neutrino-wind” scenario of core-collapse type II supernovae (SNII). Nuclear and astrophysical constraints on the reproduction of the available r-process observables will be reviewed.

Rapid neutron capture in stellar explosions is responsible for the heaviest elements in nature, up to Th , U and beyond. This nucleosynthesis process, the r-process, is unique in the sense that a combination of nuclear physics far from stability (masses, half-lives, neutron-capture and photodisintegration, neutron-induced and beta-delayed fission and last but not least neutrino-nucleus interactions) is intimately linked to ejecta from astrophysical explosions (core collapse supernovae or other neutron star related events). The astrophysics and nuclear physics involved still harbor many uncertainties, either in the extrapolation of nuclear properties far beyond present experimental explorations or in the modeling of multidimensional, general relativistic (neutrino-radiation) hydrodynamics with rotation and possibly required magnetic fields. Observational clues about the working of the r-process are mostly obtained from solar abundances and from the abundance evolution of the heaviest elements as a function of galactic age, as witnessed in old extremely metal-poor stars. They contain information whether the r-process is identical for all stellar events, how abundance features develop with galactic time and whether the frequency of r-process events is comparable to that of average core collapse supernovae - producing oxygen through titanium, as well as iron-group nuclei. The theoretical modeling of the r-process has advanced from simple approaches, where the use of static neutron densities and temperatures can aid to test the influence of nuclear properties far from stability on abundance features, to more realistic expansions with a given entropy, global neutron/proton ratio and expansion timescales, as expected from explosive astrophysical events. The direct modeling in astrophysical events such as supernovae still faces the problem whether the required conditions can be met.

Within a full dynamical parameter study including freezeout effects, we have determined the astrophysical conditions for an r-process in the so-called ``neutrino-wind`` scenario of core-collapse type II supernovae (SNII). We have started our calculations after the total photo disintegration of the matter above the nascent neutron star at 9 (.) 101 Kelvin with protons and neutrons. We have used the charged-particle network of Thielemann and the r-process code of Freiburghaus, combined with the NON-SMOKER neutron-capture rates of Rauscher, nuclear masses from the ETFS1-Q mass model and recent experimental and theoretical gross beta-decay properties. Using the three parameters V-exp (expansion speed of the shock wave), S (entropy of the bubble) and the neutron-to-proton ratio Y-e, we show that the above quantities have to fulfill specific conditions in order to make a successful r-process. According to observations and hydrodynamical simulations, respectively, a realistic value for Vexp is 7500 km/s, and Y>0.5.

Still today, the nucleosynthesis origin of Xe-H in presolar nanodiamonds is far from understood. Historically, possible explanations were proposed by a secondary "neutron-burst" process occurring in the He- or C/O-shells of a type-II supernova (SN-II), which are, however, not fully convincing in terms of modern nucleosynthesis conditions. Therefore, we have investigated Xe isotopic abundance features that may be diagnostic for different versions of a classical, primary r-process in high-entropy-wind (HEW) ejecta of core-collapse SN-II. We report here on parameter tests for non-standard r-process variants, by varying electron abundances (Y$_e$), ranges of entropies (S) and expansion velocities (V$_{exp}$) with their correlated neutron-freezeout times ($\tau$(freeze)) and temperatures (T$_9$(freeze)). From this study, we conclude that a best fit to the measured Xe-H abundance ratios $^i$Xe/$^{136}$Xe can be obtained with the high-S "main" component of a "cold" r-process variant., Comment: 7 pages, 7 figures, Seventh European Summer School on Experimental Nuclear Astrophysics, Sept. 15-27 2013, Santa Tecla (CT), Sicily, Italy

We report on a concerted effort aimed at understanding the origin and history of the pre-solar nanodiamonds in meteorites including the astrophysical sources of the observed isotopic abundance signatures. This includes measurement of light elements by secondary ion mass spectrometry (SIMS), analysis of additional heavy trace elements by accelerator mass spectrometry (AMS) and dynamic calculations of r-process nucleosynthesis with updated nuclear properties. Results obtained indicate: a) there is no evidence for the former presence of now extinct 26Al and 44Ti in our diamond samples other than what can be attributed to silicon carbide and other "impurities"; this does not offer support for a supernova (SN) origin but neither does it negate it; b) analysis by AMS of platinum in "bulk diamond" yields an overabundance of r-only 198Pt that at face value seems more consistent with the neutron burst than with the separation model for the origin of heavy trace elements in the diamonds, although this conclusion is not firm given analytical uncertainties; c) if the Xe-H pattern was established by an unadulterated r-process, it must have been a strong variant of the main r-process, which possibly could also account for the new observations in platinum., Workshop on Astronomy with Radioactvities VII; Publications of the Astronomical Society of Australia, accepted

Half-life (${T}_{1/2}$) and \ensuremath{\beta}-delayed neutron branching (${P}_{n}$) values of 492(25) ms and 49(8)$%$, 350(15) ms and 72(8)$%$, and 93(13) ms and 90(10)$%$ for the $r$-process nuclei ${}^{137,138,139}$Sb, respectively, have been measured at the CERN On-Line Isotope Mass Separator (ISOLDE) facility by counting \ensuremath{\beta}-delayed neutrons. More precise ${T}_{1/2}$ and ${P}_{n}$ values of 300(15) ms and 27(4)$%$, and 273(7) ms and 50(8)$%$ for ${}^{136,137}$Sn, respectively, have also been measured. The sources were prepared by using the selective ionization of Sb or Sn with the Resonance Ionization Laser Ion Source and the high-resolution mass separator. The new data for Sb isotopes are compared with calculated ${T}_{1/2}$ and ${P}_{n}$ values for both spherical and nonspherical shapes. The data have been incorporated into parametrized nucleosynthesis calculations of the $r$ process in high-entropy winds of core-collapse supernovae in order to study the properties of the $A$ $=$ 130 solar-system $r$-process abundance peak.

To better characterize the abundance patterns produced by the r-process, we have derived new abundances or upper limits for the heavy elements zinc (Zn), yttrium (Y), lanthanum (La), europium (Eu), and lead (Pb). Our sample of 161 metal-poor stars includes new measurements from 88 high resolution and high signal-to-noise spectra obtained with the Tull Spectrograph on the 2.7m Smith Telescope at McDonald Observatory, and other abundances are adopted from the literature. We use models of the s-process in AGB stars to characterize the high Pb/Eu ratios produced in the s-process at low metallicity, and our new observations then allow us to identify a sample of stars with no detectable s-process material. In these stars, we find no significant increase in the Pb/Eu ratios with increasing metallicity. This suggests that s-process material was not widely dispersed until the overall Galactic metallicity grew considerably, perhaps even as high as [Fe/H]=-1.4. We identify a dispersion of at least 0.5 dex in [La/Eu] in metal-poor stars with [Eu/Fe], Comment: Accepted for publication in the Astrophysical Journal. 25 pages, 13 figures

We report on a detailed abundance analysis of two strongly r-process enhanced, very metal-poor stars newly discovered in the HERES project, CS 29491-069 ([Fe/H]=-2.51, [r/Fe]=+1.1) and HE 1219-0312 ([Fe/H]=-2.96, [r/Fe]=+1.5). The analysis is based on high-quality VLT/UVES spectra and MARCS model atmospheres. We detect lines of 15 heavy elements in the spectrum of CS 29491-069, and 18 in HE 1219-0312; in both cases including the Th II 4019 {\AA} line. The heavy-element abundance patterns of these two stars are mostly well-matched to scaled solar residual abundances not formed by the s-process. We also compare the observed pattern with recent high-entropy wind (HEW) calculations, which assume core-collapse supernovae of massive stars as the astrophysical environment for the r-process, and find good agreement for most lanthanides. The abundance ratios of the lighter elements strontium, yttrium, and zirconium, which are presumably not formed by the main r-process, are reproduced well by the model. Radioactive dating for CS 29491-069 with the observed thorium and rare-earth element abundance pairs results in an average age of 9.5 Gyr, when based on solar r-process residuals, and 17.6 Gyr, when using HEW model predictions. Chronometry seems to fail in the case of HE 1219-0312, resulting in a negative age due to its high thorium abundance. HE 1219-0312 could therefore exhibit an overabundance of the heaviest elements, which is sometimes called an "actinide boost".

While the high-entropy wind (HEW) of Type II supernovae remains one of the more promising sites for the rapid neutron-capture (r-) process, hydrodynamic simulations have yet to reproduce the astrophysical conditions under which the latter occurs. We have performed large-scale network calculations within an extended parameter range of the HEW, seeking to identify or to constrain the necessary conditions for a full reproduction of all r-process residuals N_{r,\odot}=N_{\odot}-N_{s,\odot} by comparing the results with recent astronomical observations. A superposition of weighted entropy trajectories results in an excellent reproduction of the overall N_{r,\odot}-pattern beyond Sn. For the lighter elements, from the Fe-group via Sr-Y-Zr to Ag, our HEW calculations indicate a transition from the need for clearly different sources (conditions/sites) to a possible co-production with r-process elements, provided that a range of entropies are contributing. This explains recent halo-star observations of a clear non-correlation of Zn and Ge and a weak correlation of Sr - Zr with heavier r-process elements. Moreover, new observational data on Ru and Pd seem to confirm also a partial correlation with Sr as well as the main r-process elements (e.g. Eu)., Comment: 15 pages, 1 table, 4 figures; To be published in the Astrophysical Journal Letters

Since the historical papers by Burbidge et al. and Cameron 50 years ago, it is generally accepted that half of the chemical elements above Fe are formed in explosive stellar scenarios by a rapid neutron‐capture process (the classical “r‐process”). Already from their essential ideas, it became clear that a correct modelling of this nucleosynthesis process requires both, the knowledge of various nuclear properties very far from stability and a detailed description of the astrophysical environments. However, it took about three decades, until in 1986 the first experimental nuclear‐physics data on the neutron‐magic r‐isotopes 80Zn and 130Cd could be obtained, which act as key “waiting points” in the respective A≃80 and 130 peaks of the Solar‐System (SS) r‐abundances (Nr,⊙). Since then, using steadily improved nuclear data, we have optimized our r‐process calculations to reproduce the present observables of the isotopic Nr,⊙ “residuals”, as well as the more recent elemental abundances in ultra‐metal‐poor, r‐process‐enriched halo stars. Concerning the latter observations, we support the basic idea about two different types of r‐processes. Based on our many years' experience with the site‐independent “waiting‐point approach”, we recently have extended our studies to fully dynamical network calculations for the most likely astrophysical r‐process scenario, i.e. the high‐entropy wind (HEW) of core‐collapse type II supernovae (SN II). Again, an excellent reproduction of all observables for the “main” r‐process has been achieved. However, a major difference is the nucleosynthesis origin of the lighter heavy elements in the 29⩽Z⩽45 mass region. Here, the HEW model predicts—instead of a “weak” neutron‐capture r‐process component—a primary rapid charged‐particle process. This may explain the recent observations of a non‐correlation of these elements with the heavier “main” r‐process elements.

In an attempt to constrain the astrophysical conditions for the nucleosynthesis of the classical r‐process elements beyond Fe, we have performed large‐scale dynamical network calculations within the model of an adiabatically expanding high‐ entropy wind (HEW) of type II supernovae (SN II). A superposition of several entropy‐components (S) with model‐inherent weightings results in an excellent reproduction of the overall Solar System (SS) isotopic r‐process residuals (Nr,⊙), as well as the more recent observations of elemental abundances of metal‐poor, r‐process rich halo stars in the early Galaxy. For the heavy r‐process elements beyond Sn, our HEW model predicts a robust abundance pattern up to the Th, U r‐chronometer region. For the lighter neutron‐capture region, an S‐dependent superposition of (i) a normal α‐component directly producing stable nuclei, including s‐only isotopes, and (ii) a component from a neutron‐rich α‐freezeout followed by the rapid recapture of β‐delayed neutrons (βdnrpar; emitted ...

The exact conditions for the supemova high‐entropy wind (HEW) as one of the favored sites for the rapid neutron‐capture (r‐) process still cannot be reproduced self‐consistently in present hydrodynamic astrophysical models. Therefore, we have performed large‐scale dynamical network calculations within a parameterized HEW model to constrain the necessary conditions for a full r‐process and to compare our results with recent observations. A model‐inherently weighted superposition of entropy trajectories results in an excellent reproduction of the overall Solar‐System isotopic abundances (Nr,⊙) of the “main” r‐process elements beyond Sn. For the lighter r‐elements in the range 26⩽Z⩽42, our HEW model supports earlier qualitative ideas about a multiplicity of nucleosynthetic processes leading to the total Nr,⊙ distribution. In the HEW scenario, these suggestions are quantified, and the origin of the missing primary process is confirmed to be a rapid charged‐particle process, thus excluding a “weak” neutron‐capture component. This explains the recent halo‐star observations of a Z‐dependent non‐correlation, respectively partial correlation of the lighter r‐elements with metallicity and/or enrichment of “main” r‐process elements.The exact conditions for the supemova high‐entropy wind (HEW) as one of the favored sites for the rapid neutron‐capture (r‐) process still cannot be reproduced self‐consistently in present hydrodynamic astrophysical models. Therefore, we have performed large‐scale dynamical network calculations within a parameterized HEW model to constrain the necessary conditions for a full r‐process and to compare our results with recent observations. A model‐inherently weighted superposition of entropy trajectories results in an excellent reproduction of the overall Solar‐System isotopic abundances (Nr,⊙) of the “main” r‐process elements beyond Sn. For the lighter r‐elements in the range 26⩽Z⩽42, our HEW model supports earlier qualitative ideas about a multiplicity of nucleosynthetic processes leading to the total Nr,⊙ distribution. In the HEW scenario, these suggestions are quantified, and the origin of the missing primary process is confirmed to be a rapid charged‐particle process, thus excluding a “weak” neutron‐cap...

Nucleosynthesis is the science related to all astrophysical processes which are responsible for the abundances of the elements and their isotopes in the universe. The astrophysical sites are the big bang and stellar objects. The working of nucleosynthesis processes is presented in a survey of events which act as abundance sources. For intermediate-mass and heavy elements, these are stellar evolution, type Ia and core collapse supernovae as well as hypernovae. We discuss successes and failures of existing processes and possible solutions via new (hitherto unknown) processes. Finally an analysis of their role is given in the puzzle to explain the evolution of the elemental and isotopic compositions found in galaxies, and especially the mixture found in the solar system. Different timescales due to the progenitor mass dependence of the endpoints of stellar evolution (type II supernova explosions — SNe II vs. planetary nebulae) or single vs. binary stellar systems (the latter being responsible for novae, type Ia supernovae — SNe Ia, or X-ray bursts) are the keys to understand galactic evolution. At very early times, the role of explosion energies of events, polluting pristine matter with a composition originating only from the big bang, might also play a role. We also speculate on the role of very massive stars not undergoing SN II explosions but rather causing “hypernovae” after the formation of a central black hole via core collapse.

Theoretical studies of the nucleosynthesis origin of the heavy elements in our Solar System (S.S.) by the rapid neutron-capture process (r-process) still face the entwined uncertainties in the possible astrophysical scenarios and the nuclear-physics properties far from stability. In this paper we present results from the investigation of an r-process in the high-entropy wind (HEW) of core-collapse supernovae (here chosen as one of the possible scenarios for this nucleosynthesis process), using new nuclear-data input calculated in a consistent approach, for masses and $\beta$-decay properties from the new finite-range droplet model FRDM(2012). The accuracy of the new mass model is 0.56 MeV with respect to {\sc AME2003}, to which it was adjusted. We compare the new HEW r-process abundance pattern to the latest S.S. r-process residuals and to our earlier calculations with the nuclear-structure quantities based on FRDM(1992). Substantial overall and specific local improvements in the calculated pattern of the r-process between $A\simeq 110$ and $^{209}$Bi, as well as remaining deficiencies are discussed in terms of the underlying spherical and deformed shell structure far from stability., Comment: 8 pages, 4 figures

The processes discussed in this review are three of the four nucleosynthesis processes involved in producing heavy nuclei beyond Fe (not counting the rp-process in X-ray bursts). Opposite to the fourth process (the s-process), which operates in stellar evolution during He- and C-burning, they are all related to explosive burning phases, (presumably) linked to core collapse supernova events of massive stars. The (classical) p-process is identified with explosive Ne/O-burning in outer zones of the progenitor star. It is intitiated by the passage of the supernova shock wave and acts via photodisintegration reactions like a spallation process which produces neighboring (proton-rich) isotopes from pre-existing heavy nuclei. The reproduction of some of the so-called lighter p-isotopes with A < 100 faces problems in this environment. The only recently discovered ?p-process is related to the innermost ejecta, the neutrino wind expelled from the hot proto-neutron star after core collapse in the supernova explosion. This neutrino wind is proton-rich in its early phase and reactions with neutrinos permit to overcome decay/reaction bottlenecks for the flow beyond the Fe-group, thus permitting the production of those p-isotopes, which face problems in the classical p-process scenario. The understanding of the r-process, being identified for a long time with rapid neutron captures ? and passing through nuclei far from stability ? is still experiencing major problems. These are on the one hand related to nuclear uncertainties far from stability (masses and half-lives), affecting the process speed and abundance peaks, on the other hand the site is still not definitely located, yet. Later neutron-rich, high entropy phases of the neutrino wind could permit its operation, other options include the ejection of very neutron-rich neutron star matter. Two different environments are required for a weak and a main/strong r-process, witnessed by observations of low metallicity stars.