出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：Evolved low- and intermediate-mass stars are important sites for the production of heavy nuclei (through slow n-captures) and of light- and intermediate-mass isotopes (through p-captures). This was revealed by spectroscopy of evolved stars as well as by the chemical analysis of presolar grains of circumstellar origins. The observational basis for these issues has grown considerably over the years, confirming peculiar abundances of 3He, 7Li, CNO isotopes and 26Al. Many studies have been presented in the last thirty years suggesting that the above evidence can be accounted for by non-convective transportmechanisms that link the stellar envelopewith the region where pcaptures take place, during the red giant phases. Nucleosynthesis in deep mixing episodes is made uncertain by two series of problems. On one side one has to identify the physical mechanism for the transport. On the other, several reaction rates adopted in the calculations are still uncertain, mainly because hydrogen burning takes place in red giants at typical Gamov-Peak energies of a few tens of keV, where experimental measurements are extremely difficult. We show how the use of recent and accurate reaction rates induces considerable differences in the nucleosinthesis results as compared to previous studies. Among the most remarkable novelties we discuss the effects of the new rates for the 14N(p,g )15O and for p-captures on oxygen isotopes. They jointly provide a much better agreement than before with presolar grain isotopic abundances and allow for a clear determination of the mass of the parent star.
