Nuclear reactions and stellar processes

Nuclear Astrophysics is concerned with the study of nuclear processes at stellar temperature and density conditions. A main goal is the understanding of the synthesis of the elements and the generation of energy guiding stellar evolution and driving stellar explosions. Observables (like e.g. luminosity curves or elemental abundance distributions) witness the interplay between nuclear structure aspects near the particle drip-lines and the appropriate astrophysical environments, and give guidance to and constraints on stellar conditions and the associated nucleosynthesis. We present an overview of the broad range of nucleosynthesis scenarios from the Big Bang to the different conditions during stellar evolution and stellar explosion. Special emphasis is given to the discussion of nuclear physics aspects of pre-supernova collapse and supernova shock front nucleosynthesis. Of great interests are presently nucleosynthesis processes far from the limits of stability like the neutron driven r-process and the hydrogen driven rp-process. The nuclear physics of the r-process and the possible site for the r-process in the neutrino driven wind of the supernova shock are discussed and the possible impact of neutrino induced processes is presented. Hydrogen induced explosive processes occur in the thermonuclear runaway on the surface of accreting compact stars at electron degenerate conditions. This includes novae triggered by accretion on white dwarfs and x-ray bursts initiated by accretion on neutron stars. High accretion rates on white dwarfs and neutron stars lead to supernova type Ia explosions or to x-ray pulsars respectively. An overview of the nucleosynthesis conditions and uncertainties is given for all of these scenarios. (author)