Heavy Element Nucleosynthesis

Mounib F El Eid,C Spitaleri,G Rapisarda,L Lamia,R.G Pizzone,M.L Sergi

doi:10.1051/epjconf/201818401007

Abstract

This contribution deals with the important subject of the nucleosynthesis of heavy elements in the Galaxy. After an overview of several observational features, the physical processes responsible mainly for the formation of heavy elements will be described and linked to possible stellar sites and to galactic chemical evolution. In particular, we focus on the neutron-capture processes, namely the s-process (slow neutron capture) and the r-process (rapid neutron capture) and discuss some problems in connection with their sites and their outcome. The aim is to give a brief overview on the exciting subject of the heavy element nucleosynthesis in the Galaxy, emphasizing its importance to trace the galactic chemical evolution and illustrating the challenge of this subject.

Highlights

Elements formation and their evolution is linked to stellar evolution
A convenient way of studying the heavy element synthesis is to see their traces in metalpoor halo stars
The presence of heavy elements in these stars indicate the role of a distinct generation of massive stars stars, which were able to synthesize the observed heavy elements

Summary

Introduction

Elements formation and their evolution is linked to stellar evolution. Fusion reactions can synthesize elements up to Iron, which is the branching point between fusion and fission. The synthesis of elements is possible only through neutron capture reactions, since neutrons do not experience a coulomb barrier. The main neutron-capture processes are known to be the slow s-process and the rapid r-process. Both of them occur during the late evolutionary phases of stars. A convenient way of studying the heavy element synthesis is to see their traces in metalpoor halo stars. Their chemical compositions indicates the types of syntheses that happen in the early galaxy. This is a link to “near-field cosmology”, or low-red shift universe. We have the primordial nucleosynthesis, the microwave back ground radiation and the Hubble expansion, which help us to draw conclusion about the early universe

Observations

Basic comments on the s-process and r-process

Comments on the s-process

Comments on the r-process

Stellar Sites

Brief Summary