Astrophysical relevance of γ\gamma transition energies

The relevant gamma energy range is explicitly identified where additional gamma$ strength has to be located for having an impact on astrophysically relevant reactions. It is shown that folding the energy dependences of the transmission coefficients and the level density leads to maximal contributions for gamma energies of 2<=E_gamma<=4 MeV unless quantum selection rules allow isolated states to contribute. Under this condition, electric dipole transitions dominate. These findings allow to more accurately judge the relevance of modifications of the \gamma strength for astrophysics.Comment: 5 pages, 11 figures, version accepted as a Rapid Communication in Phys. Rev.

Proton-rich nucleosynthesis and nuclear physics

Although the detailed conditions for explosive nucleosynthesis are derived from astrophysical modeling, nuclear physics determines fundamental patterns in abundance yields, not only for equilibrium processes. Focussing on the nu p- and the gamma-process, general nucleosynthesis features within the range of astrophysical models, but (mostly) independent of details in the modelling, are presented. Remaining uncertainties due to uncertain Q-values and reaction rates are discussed

Radiogenic p-isotopes from type Ia supernova, nuclear physics uncertainties, and galactic chemical evolution compared with values in primitive meteorites

The nucleosynthesis of proton-rich isotopes is calculated for multi-dimensional Chandrasekhar-mass models of Type Ia supernovae (SNe Ia) with different metallicities. The predicted abundances of the short-lived radioactive isotopes 92Nb, 97, 98Tc, and 146Sm are given in this framework. The abundance seeds are obtained by calculating s-process nucleosynthesis in the material accreted onto a carbon-oxygen white dwarf from a binary companion. A fine grid of s-seeds at different metallicities and 13C-pocket efficiencies is considered. A galactic chemical evolution model is used to predict the contribution of SN Ia to the solar system p-nuclei composition measured in meteorites. Nuclear physics uncertainties are critical to determine the role of SNe Ia in the production of 92Nb and 146Sm. We find that, if standard Chandrasekhar-mass SNe Ia are at least 50% of all SN Ia, they are strong candidates for reproducing the radiogenic p-process signature observed in meteorites.Peer reviewedFinal Accepted Versio

Measurement of (α,n) reaction cross sections of erbium isotopes for testing astrophysical rate predictions

Date of Acceptance: 30/01/2015The γ-process in core-collapse and/or type Ia supernova explosions is thought to explain the origin of the majority of the so-called p nuclei (the 35 proton-rich isotopes between Se and Hg). Reaction rates for γ-process reaction network studies have to be predicted using Hauser-Feshbach statistical model calculations. Recent investigations have shown problems in the prediction of α-widths at astrophysical energies which are an essential input for the statistical model. It has an impact on the reliability of abundance predictions in the upper mass range of the p nuclei. With the measurement of the 164,166Er(α,n)167,169Yb reaction cross sections at energies close to the astrophysically relevant energy range we tested the recently suggested low energy modification of the α+nucleus optical potential in a mass region where γ-process calculations exhibit an underproduction of the p nuclei. Using the same optical potential for the α-width which was derived from combined 162Er(α,n) and 162Er(α,γ) measurement makes it plausible that a low-energy modification of the optical α+nucleus potential is needed.Peer reviewedFinal Accepted Versio

Reaction Rates and Nuclear Properties Relevant for Nucleosynthesis in Massive Stars and Far From Stability

Explosive nuclear burning in astrophysical environments produces unstable nuclei which again can be targets for subsequent reactions. In addition, it involves a large number of stable nuclides which are not fully explored by experiments, yet. Thus, it is necessary to be able to predict reaction cross sections and thermonuclear rates with the aid of theoretical models. Such predictions are also of interest for investigations at radioactive ion beam facilities. An extended library of theoretical cross sections and reaction rates is presented. The problem of alpha+nucleus potentials is addressed and new parametrizations presented. The problem of properly predicting cross sections at low level densities is illustrated by the 62Ni(n,gamma) reaction.Comment: 7 pages, invited talk, to appear in proceedings of CGS11 (Prague), World Scientific (new version: fixed typo in potential parameters; note: they will still be incorrect in the printed version

Testing the role of SNe Ia for galactic chemical evolution of p-nuclei with two-dimensional models and with s-process seeds at different metallicities

Date of Acceptance: 07/11/2014The bulk of p isotopes is created in the "gamma processes" mainly by sequences of photodisintegrations and beta decays in explosive conditions in Type Ia supernovae (SNIa) or in core collapse supernovae (ccSN). The contribution of different stellar sources to the observed distribution of p-nuclei in the solar system is still under debate. We explore single degenerate Type Ia supernovae in the framework of two-dimensional SNIa delayed-detonation explosion models. Travaglio et al. discussed the sensitivity of p-nuclei production to different SNIa models, i.e., delayed detonations of different strength, deflagrations, and the dependence on selected s-process seed distributions. Here we present a detailed study of p-process nucleosynthesis occurring in SNIa with s-process seeds at different metallicities. Based on the delayed-detonation model DDT-a of TRV11, we analyze the dependence of p-nucleosynthesis on the s-seed distribution obtained from different strengths of the 13C pocket. We also demonstrate that 208Pb seed alone changes the p-nuclei production considerably. The heavy-s seeds (140 ≤A < 208) contribute with about 30%-40% to the total light-p nuclei production up to 132Ba (with the exception of 94Mo and 130Ba, to which the heavy-s seeds contribute with about 15% only). Using a Galactic chemical evolution code from Travaglio et al., we study the contribution of SNIa to the solar stable p-nuclei. We find that explosions of Chandrasekhar-mass single degenerate systems produce a large amount of p-nuclei in our Galaxy, both in the range of light (A ≤ 120) and heavy p-nuclei, at almost flat average production factors (within a factor of about three). We discussed in details p-isotopes such as 94Mo with a behavior diverging from the average, which we attribute to uncertainties in the nuclear data or in SNIa modeling. Li et al. find that about 70% of all SNeIa are normal events. If these are explained in the framework of explosions of Chandrasekhar-mass white dwarfs resulting from the single-degenerate progenitor channel, we find that they are responsible for at least 50% of the p-nuclei abundances in the solar system.Peer reviewedFinal Accepted Versio

Production of 92Nb, 92Mo, and 146Sm in the gamma-process in SNIa

The knowledge of the production of extinct radioactivities like 92Nb and 146Sm by photodisintegration processes in ccSN and SNIa models is essential for interpreting abundances in meteoritic material and for Galactic Chemical Evolution (GCE). The 92Mo/92Nb and 146Sm/144Sm ratios provide constraints for GCE and production sites. We present results for SNIa with emphasis on nuclear uncertainties.Comment: 6 pages, 4 figures, Proceedings of the 13th Symposium on Nuclei in the Cosmos (NIC XIII), July 2014, Debrecen, Hungar

70Ge(p,gamma)71As and 76Ge(p,n)76As cross sections for the astrophysical p process: sensitivity of the optical proton potential at low energies

The cross sections of the 70Ge(p,gamma)71As and 76Ge(p,n)76As reactions have been measured with the activation method in the Gamow window for the astrophysical p process. The experiments were carried out at the Van de Graaff and cyclotron accelerators of ATOMKI. The cross sections have been derived by measuring the decay gamma-radiation of the reaction products. The results are compared to the predictions of Hauser-Feshbach statistical model calculations using the code NON-SMOKER. Good agreement between theoretical and experimental S factors is found. Based on the new data, modifications of the optical potential used for low-energy protons are discussed.Comment: Accepted for publication in Phys. Rev.

The Eclipse Mapping Null Space: Comparing Theoretical Predictions with Observed Maps

High-precision exoplanet eclipse light curves, like those possible with JWST, enable flux and temperature mapping of exoplanet atmospheres. These eclipse maps will have unprecedented precision, providing an opportunity to constrain current theoretical predictions of exoplanet atmospheres. However, eclipse mapping has unavoidable mathematical limitations because many map patterns are unobservable. This ``null space'' has implications for making comparisons between predictions from general circulation models (GCMs) and the observed planet maps, and, thus, affects our understanding of the physical processes driving the observed maps. We describe the eclipse-mapping null space and show how GCM forward models can be transformed to their observable modes for more appropriate comparison with retrieved eclipse maps, demonstrated with applications to synthetic data of an ultra-hot Jupiter and a cloudy warm Jupiter under JWST-best-case- and extreme-precision observing scenarios. We show that the effects of the null space can be mitigated and manipulated through observational design, and JWST exposure times are short enough to not increase the size of the null space. Furthermore, we show the mathematical connection between the null space and the ``eigenmapping'' method, demonstrating how eigenmaps can be used to understand the null space in a model-independent way. We leverage this connection to incorporate null-space uncertainties in retrieved maps, which increases the uncertainties to now encompass the ground truth for synthetic data. The comparisons between observed maps and forward models that are enabled by this work, and the improved eclipse-mapping uncertainties, will be critical to our interpretation of multidimensional aspects of exoplanets in the JWST era.Comment: 20 pages, 12 figures. Accepted for publication in The Astronomical Journal. Note that PDF readers may blur figures 1 and 3, which can be fixed by zooming i

Observing Nucleon Decay in Lead Perchlorate

Lead perchlorate, part of the OMNIS supernova neutrino detector, contains two nuclei, 208Pb and 35Cl, that might be used to study nucleon decay. Both would produce signatures that will make them especially useful for studying less-well-studied neutron decay modes, e.g., those in which only neutrinos are emitted.Comment: 6 pages, 2 figure