IReNA Online Seminar featuring Stephane Goriely (University libre de Bruxelles)

Title: Some Open Questions Related to the Nucleosynthesis of the Heavy Elements

Abstract: One of the major issues in modern astrophysics concerns the analysis of the present
composition of the Universe and its various constituting objects. The composition of the various
constituents of the Universe at the galactic and stellar scales has evolved since the Big Bang.
The study of this evolution has been the subject of an enormous amount of observational, experimental
and theoretical work. Nucleosynthesis models aim to explain the origin of the different
nuclei observed in nature by identifying the possible processes able to synthesize them.

Though the origin of most of the nuclides lighter than iron is now quite well understood,
the synthesis of the heavy elements (i.e. heavier than iron) remains puzzling in many respects.
The major mechanisms called for to explain the production of the heavy nuclei are the slow
neutron-capture process (or s-process), occurring during the hydrostatic stellar burning phases,
the rapid neutron-capture process (or r-process) believed to develop during the explosion of a
star as a supernova or the coalescence of two binary neutron stars. In addition, the origin of the
neutron-deficient nuclides observed in the solar system is attributed to the so-called p-process
taking place in supernovae. Though these processes have been quite successful in explaining the
many observations available, each of them is still subject to key open questions, both from the
astrophysical and nuclear physics modelling. In addition, a number of spectroscopic observations
are still challenging our nucleosynthesis models. These concern in particular the Chemically
Peculiar (CP) stars and the recently discovered P-rich stars. In these cases, non-thermal
nucleosynthesis may provide some interesting features and could open new interesting future avenues
both for astrophysics and nuclear physics.