Preisträgervorträge

Preisträgervortrag

Nucleosynthesis of intermediate and heavy elements in Supernova

Gabriel Martinez-Pinedo

The main processes determining the nucleosynthesis of elements were already reviewed by Burbidge, Burbidge, Fowler and Hoyle and indepently by Cameron in 1957 but many open issues remain till today related to the nucleosynthesis of intermediate and heavy elements in supernovae. A core-collapse supernova explosion occurs when the iron core of a massive star becomes unstable and collapses to produce a neutron star. The liberated energy, mainly in neutrinos, heats the material surrounding the newly born neutron star to such a large temperatures that matter is completely dissociated. As the ejected matter expands and cools nucleons reassemble into nuclei. The composition of this matter depends of the ratio of protons to neutrons that is determined by the spectra and luminosities of the emitted (anti)neutrinos. Modern supernova simulations show that the early ejecta are proton rich. These ejecta are the site of a new nucleosynthesis process that we have denoted vp-process. In this process, the assembled nuclei have equal number of neutrons and protons with large beta decay half-lives and low proton capture probabilities which would inhibit the creation of heavier elements. However, the matter is under a strong antineutrino flux that converts some of the free protons into neutrons. These neutrons are immediately absorbed by the neutron deficient nuclei allowing for subsequent proton captures. In this way, isotopes like ^92,94Mo and ^96,98Ru can be synthesized whose production has long been a mystery.