Nucleosynthesis in massive stars using extended adaptive nuclear reaction networks

We present the first calculations to follow the evolution of all stable isotopes and their abundant radioactive progenitors in a finely zoned stellar model from the onset of central hydrogen burning through explosion as a Type II supernova. An extended adaptive nuclear reaction network is implemented that contains about 700 isotopes during hydrogen and helium burning and more than 2500 isotopes during the supernova explosion. The calculations were performed for 15, 20, and 25 M-circle dot Pop I stars using the most recently available set of experimental and theoretical nuclear data. We include revised opacity tables, take into account mass loss due to stellar winds, and implement revised weak interaction rates that significantly affect the properties of the presupernova core.

An s-process is present, which, along with the usual nucleosynthesis from advanced burning stages and the explosion, produces nearly solar abundances for most nuclei up to A = 60 in the 25 M-circle dot star. Between A = 60 and A = 90 we find that the s-process leads to an over-production of key nuclei by a factor similar to 2 - 3. Above A = 90 the s-process has makes little contribution, but we find the approximately solar production of many proton-rich isotopes above mass number A = 120 due to the gamma -process.