The reaction flow during explosive nuclear burning on an accreting neutron star

This dissertation contains the first extensive investigation of the detailed reaction flow of an X-ray burst under realistic conditions. It was made possible by building a new computational model. This model distinguishes itself by introducing for the first time: full general relativistic (GR) hydrodynamical equations, GR corrected atmosphere, GR corrected convection, modern approximations of the opacities and conductivities, neutrino losses, and a GR inner boundary of the core luminosity. We use conservative equations allowing a precise tracking off all released energy which reveals unprecedented details in the luminosity. The simulations show that – • An interplay between the helium flash and the rp-process produces an identifiable double-peaked structure, which has been observed. • The burst temperature is lower than previously assumed, so the Tecycle is not reached. The average mass of the ashes is ∼ 64. Carbon is destroyed by helium captures before reaching the ocean. • Convection does not hit the surface for mixed hydrogen/helium bursts. Therefore we predict that burst spectral lines are not from material from deeper layers. • Convection extends to the surface in helium ignited bursts. We predict a sudden rise in helium and sulfur as the turbulent overturn breaches the surface. We also give a complete description of the X-rat burst reaction flow including branchings and waiting points as a guide to future experiments and observations.