The production of heavy elements in the cosmos (FA 32)
by
Friedrich-Karl Thielemann(University of Basel)
→
Europe/Stockholm
FA 32
FA 32
Description
The US National Research Council's Committee on Physics of the Universe posed 11 most important questions for the 21st century: 1. What is dark matter, 2. what is dark energy, 3. how were the heavy elements from Fe to Uranium made, ....?
The solar abundances of elements beyond H, He, and Li are the result of an integration over Galactic evolution with its different contributing sources (ejecta from stellar winds or explosions) as a function of time (and metallicity). The elements of the “Fe-group” (Ti to Zn) originate from explosive high-temperature burning in type Ia (thermonuclear) and core collapse supernovae from massive stars. Heavier elements result dominantly from environments permitting neutron capture, either under conditions where neutron capture is slow in comparison to beta-decays (s-process) or rapid (r-process). The s-process points to a process with a nucleosynthesis path in the chart of nuclei which experiences closed neutron shells (magic numbers) among stable nuclei, and abundance peaks are due to small neutron capture rates at these points. For the r-process this happens for very neutron-rich isotopes far from stability, and the peaks are due to long beta-decay half-lives. In combination, both processes explain the double-peak structure of solar abundances. We know that the s-process has different contributions from massive and low/intermediate mass stars and varies with metallicity. “Solar” s-abundances result only from integrating over all these con- tributions. Early observations seemed to indicate that the r-process was a unique event, always (re-)producing the “solar” r-process abundance pattern. However, most recent observations also point to a superposition of at least two types of processes, and thus contributions from different sources. We will discuss three options (i) the high entropy neutrino wind in supernovae, (ii) neutron-star mergers in binary systems, and (iii) jets from core collapses with high rotation rates and magnetic fields.
We try to present these aspects in a survey, and approach the question which constraints are provided for astrophysical sites as well as nuclear structure by observed abundance features.
(host: S. Rosswog)
