Determination of Solar System R-Process Abundances using ENDF/B-VIII.0 and TENDL-2015 libraries

Abstract

Recent multi-messenger detection of the binary neutron star merger (GW170817) energized the astrophysical community and encouraged further research for determination of nuclear physics observables. Comprehensive studies of atomic nuclei in the cosmos provide an opportunity for investigating these astrophysical phenomena and acquiring complementary information on stellar nucleosynthesis processes that can be verified using the latest nuclear data.Evaluated Nuclear Data File (ENDF) libraries contain complete collections of reaction cross sections over the energy range relevant to astrophysics, fission yields and decay data. These data collections have been used worldwide in nuclear science, industry and national security applications. There is great interest in exploring the ENDF/B-VIII.0 and TALYS Evaluated Nuclear Data Library (TENDL-2015) for nuclear astrophysics purposes and comparing findings with the Karlsruhe Astrophysical Database of Nucleosynthesis in Stars (KADoNiS).The Maxwellian-averaged cross sections (MACS) and astrophysical reaction rates have been calculated using the ENDF/B-VIII.0 and TENDL-2015 evaluated data sets. The calculated cross sections were combined with the solar system abundances and fitted using the classical model of stellar nucleosynthesis. Astrophysical rapid-and slow-neutron capture, r-and s-process, respectively, abundances were obtained from present data and compared with available values. Further analysis of MACS reveals potential evaluated libraries data deficiencies and a strong need for new measurements. The current results demonstrate a large nuclear astrophysics potential of evaluated libraries and mutually beneficial relations between nuclear industry and research efforts.

Solar data uncertainty impacts on MCMC methods for r-process nucleosynthesis

“…Since the Solar r-process abundances are in actuality the 'residual' abundances remaining after subtracting the predicted s-process contribution from the total Solar inventory, our understanding of the Solar System r-process content is directly dependent on uncertainties in s-process nucleosynthesis predictions. More recent evaluations have demonstrated the importance of accounting for new neutron capture measurements [34] and more sophisticated treatments of the s-process astrophysical site [35]. Nevertheless, the r-process community remains in need of updated Solar s-process subtractions which put together all such new information while also carefully propagating the uncertainties associated with the meteoritic and spectroscopic data which are used to determine the total abundances of Solar System heavy elements.…”

Capture rates of highly degenerate neutrons

“…While large scale neutron capture rate compilations [13,14] based on Maxwellian averaged cross sections applicable to stellar helium burning and typical r-process sites are readily available [15][16][17][18], there is a scarcity in studies relevant to accreting neutron stars where neutron degeneracy has a stronger impact. Neutron degeneracy has been demonstrated to have a large effect on capture rates for Mg and Ca isotopes, together with plasma effects due to the degenerate electron gas [19].…”