Marcel Arnould

Databases and tools for nuclear astrophysics applications - BRUSsels Nuclear LIBrary (BRUSLIB), Nuclear Astrophysics Compilation of REactions II (NACRE II) and Nuclear NETwork GENerator (NETGEN)

An update of a previous description of the BRUSLIB + NACRE package of nuclear data for astrophysics and of the web-based nuclear network generator NETGEN is presented. The new version of BRUSLIB contains the latest predictions of a wide variety of nuclear data based on the most recent version of the Brussels-Montreal Skyrme-Hartree-Fock-Bogoliubov model. The nuclear masses, radii, spin/parities, deformations, single-particle schemes, matter densities, nuclear level densities, E1 strength functions, fission properties, and partition functions are provided for all nuclei lying between the proton and neutron drip lines over the 8 ≤ Z ≤ 110 range, whose evaluation is based on a unique microscopic model that ensures a good compromise between accuracy, reliability, and feasibility. In addition, these various ingredients are used to calculate about 100 000 Hauser-Feshbach neutron-, proton-, α-, and γ-induced reaction rates based on the reaction code TALYS. NACRE is superseded by the NACRE II compilation for 15 charged-particle transfer reactions and 19 charged-particle radiative captures on stable targets with mass numbers A < 16. NACRE II features the inclusion of experimental data made available after the publication of NACRE in 1999 and up to 2011. In addition, the extrapolation of the available data to the very low energies of astrophysical relevance is improved through the systematic use of phenomenological potential models. Uncertainties in the rates are also evaluated on this basis. Finally, the latest release v10.0 of the web-based tool NETGEN is presented. In addition to the data already used in the previous NETGEN package, it contains in a fully documented form the new BRUSLIB and NACRE II data, as well as new experiment-based radiative neutron capture cross sections. The full new versions of BRUSLIB, NACRE II, and NETGEN are available electronically from the nuclear database at http://www. astro.ulb.ac.be/NuclearData. The nuclear material is presented in an extended tabular form complemented with a variety of graphical interfaces.

Importance of the photo-beta process for the synthesis of "p" elements in stellar conditions

Abstract In this work, we compare positon capture and photo-beta disintegration probabilities in several stellar conditions. We show that the second process can be neglected with regard to the first one in strongly endothermic nuclear transitions, whereas photo-beta disintegration can be competitive with positon capture and even can have a greater likelihood than the latter process in weakly endothermic and exothermic transitions. In the range of temperature we consider here ( T ≈ 10 9 °K), it appears that the lifetime ratio τ( ph ) τ( e c + ) against photo-beta disintegration and positon capture is the smallest for densities in the neighbourhood of 10 6 g/cm 3 . Thus, we arrive at the conclusion that the photo-beta process can play a role in the synthesis of two “p” elements at least, 62 144 Sm and 80 196 Hg, for which the ratios τ( ph ) τ( e c + ) are close to 10 and 20, respectively, in the most favourable stellar conditions.

The r-Process of Nucleosynthesis: The Puzzle Is Still with Us

Through the increasing number and quality of astronomical observations, our picture of the composition of the various constituents of the Universe is getting quickly more and more complete, and concomitantly more and more complex. Despite this spectacular progress, the solar system (hereafter SoS) continues to provide a body of abundance data whose quantity, quality and coherence remain unmatched. This concerns especially the heavy elements (defined here as those with atomic numbers in excess of the value Z = 26 corresponding to iron), and in particular their isotopic compositions, which are the prime fingerprints of astrophysical nuclear processes. Except in a few cases, these isotopic patterns indeed remain out of reach even of the most-advanced stellar spectroscopic techniques available today. No wonder then that, from the early days of its development, the theory of nucleosynthesis has been deeply rooted in the SoS composition, especially in the heavy element domain.

News from the p-process: Is the s-process a troublemaker?

The most detailed calculations of the p-process call for its development in the O/Ne layers of Type II supernovae. In spite of their overall success in reproducing the solar system content of p-nuclides, they suggest a significant underproduction of the light Mo and Ru isotopes. On grounds of a model for the explosion of a 25 M⊙ star with solar metallicity, we demonstrate that this failure might just be related to the uncertainties left in the rate of the 22Ne (α, n) 25Mg neutron producing reaction. The latter indeed has a direct impact on the distribution of the s-process seeds for the p-process.

Nuclear reactions in astrophysics: recent experimental and theoretical studies, and further quests☆

Abstract A brief review is presented of recent theoretical and experimental efforts that have led to an improvement in our knowledge of nuclear reaction rates of interest in astrophysics. Emphasis is also put on the still existing (sometimes very large) uncertainties that affect some important rates. This is especially the case when short-lived nuclei are involved in the entrance channel.

NACRE II: an update and extension of the NACRE compilation of charged-particle-induced thermonuclear reaction rates for astrophysics

The status of a new evaluation of astrophysical nuclear reaction rates, referred as NACRE-II, is reported. It includes 19 radiative capture and 15 transfer reactions on targets with mass numbers A < 16. This work is meant to supersede the NACRE compilation. Post-NACRE experimental data are taken into account. Extrapolations of the astrophysical S-factor to largely sub-Coulomb energies are based on the use of the potential model and of the distorted wave Born approximation (DWBA) for capture and transfer reactions, respectively. Adopted rates and their lower and upper limits are provided. Here, we illustrate with some results the general procedure followed in the construction of NACRE-II.

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

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.