Explosive nucleosynthesis close to the drip lines

Abstract

We give an overview of explosive burning and the role which neutron and/or proton separation energies play. We focus then on the rapid neutron capture process (r-process) which encounters unstable nuclei with neutron separation energies in the range 1-4 MeV, and the rapid proton capture process (rp-process), operating close to the proton drip-line. The site of the rp-process is related to hydrogen accreting neutron stars in binary stellar systems. Explosive II-burning produces nuclei as heavy as A=100, powering events observable as X-ray bursts. The r-process abundances witness nuclear structure far from beta-stability as well as the conditions in the appropriate astrophysical environment. But there is a remaining lack in the full understanding of its astrophysical origin, ranging from the high entropy neutrino wind, blown from hot neutron star surfaces after a supernova explosion, to low entropy "cold decompresssion" of neutron star matter ejected in mergers of binary neutron star systems.