We provide a set of stellar evolution and nucleosynthesis calculations that applies established physics assumptions simultaneously to low- and intermediate-mass and massive star models. Our goal is to provide an internally consistent and comprehensiv
e nuclear production and yield data base for applications in areas such as pre-solar grain studies. Our non-rotating models assume convective boundary mixing where it has been adopted before. We include 8 (12) initial masses for $Z = 0.01$ ($0.02$). Models are followed either until the end of the asymptotic giant branch phase or the end of Si burning, complemented by a simple analytic core-collapse supernova models with two options for fallback and shock velocities. The explosions show which pre-supernova yields will most strongly be effected by the explosive nucleosynthesis. We discuss how these two explosion parameters impacts the light elements and the $s$ and $p$ process. For low- and intermediate-mass models our stellar yields from H to Bi include the effect of convective boundary mixing at the He-intershell boundaries and the stellar evolution feedback of the mixing process that produces the $^{13}$C pocket. All post-processing nucleosynthesis calculations use the same nuclear reaction rate network and nuclear physics input. We provide a discussion of the nuclear production across the entire mass range organized by element group. All our stellar nucleosynthesis profile and time evolution output is available electronically, and tools to explore the data on the NuGrid VOspace hosted by the Canadian Astronomical Data Centre are introduced.
The goal of this paper is to analyze the impact of a primary neutron source on the s-process nucleosynthesis in massive stars at halo metallicity. Recent stellar models including rotation at very low metallicity predict a strong production of primary
N14. Part of the nitrogen produced in the H-burning shell diffuses by rotational mixing into the He core where it is converted to Ne22 providing additional neutrons for the s process. We present nucleosynthesis calculations for a 25 Msun star at [Fe/H] = -3, -4, where in the convective core He-burning about 0.8 % in mass is made of primary Ne22. The usual weak s-process shape is changed by the additional neutron source with a peak between Sr and Ba, where the s-process yields increase by orders of magnitude with respect to the yields obtained without rotation. Iron seeds are fully consumed and the maximum production of Sr, Y and Zr is reached. On the other hand, the s-process efficiency beyond Sr and the ratio Sr/Ba are strongly affected by the amount of Ne22 and by nuclear uncertainties, first of all by the Ne22(alpha,n)Mg25 reaction. Finally, assuming that Ne22 is primary in the considered metallicity range, the s-process efficiency decreases with metallicity due to the effect of the major neutron poisons Mg25 and Ne22. This work represents a first step towards the study of primary neutron source effect in fast rotating massive stars, and its implications are discussed in the light of spectroscopic observations of heavy elements at halo metallicity.
