Astrophysics studies relevant to stellar x-ray bursts

Two reactions of O-14(alpha,p)(17) F and Ne-18(alpha,p)Na-21 provide the pathways for breakout from the hot CNO cycles to the rp-process in type I X-ray bursts. To better determine their astrophysical reaction rates, resonance parameters of the compound nuclei I8Ne and 22Mg have been investigated by the resonant elastic scattering of F-17+p and Na-21+p, respectively. The F-17+p and Na-21+p radioactive ion beams were produced at the CNS Radioactive Ion Beam Separator and impinged on the thick proton targets. The excitation functions were obtained with a thick-target method over a wide excitation energy range. The resonance parameters in the compound nuclei Ne-18 and Mg-22 have been determined through an R-matrix analysis. New reaction rates of these two (alpha,p) reactions are recalculated. The astrophysical impact for the Ne-18(alpha,p)Na-21 reaction has been investigated through one-zone postprocessing X-ray burst calculations.