We address the deficiency of odd-Z elements P, Cl, K and Sc in Galactic chemical evolution models through an investigation of the nucleosynthesis of interacting convective O and C shells in massive stars. 3D hydrodynamic simulations of O-shell convection with moderate C-ingestion rates show no dramatic deviation from spherical symmetry. We derive a spherically averaged diffusion coefficient for 1D nucleosynthesis simulations, which show that such convective-reactive ingestion events can be a production site for P, Cl, K and Sc. An entrainment rate of 10-3M⊙ s-1 features overproduction factors OPs ≈ 7. Full O-C shell mergers in our 1D stellar evolution massive star models have overproduction factors OPm > 1 dex but for such cases 3D hydrodynamic simulations suggest deviations from spherical symmetry. γ - process species can be produced with overproduction factors of OPm > 1 dex, for example, for 130, 132Ba. Using the uncertain prediction of the 15M⊙, Z = 0.02 massive star model (OPm ≈ 15) as representative for merger or entrainment convective-reactive events involving O- and C-burning shells, and assume that such events occur in more than 50 per cent of all stars, our chemical evolution models reproduce the observed Galactic trends of the odd-Z elements.
|Original language||English (US)|
|Journal||Monthly Notices of the Royal Astronomical Society: Letters|
|State||Published - Feb 1 2018|
Bibliographical noteFunding Information:
We acknowledge support from National Science Foundation (NSF) grant PHY-1430152, Canadian Institute for Theoretical Astrophysics, the Fonds de Recherche du Québec-Nature et technologies postdoctoral, NSF grants 1413548 and 1515792, Natural Sciences and Engineering Research Council of Canada, the Swiss National Science Foundation, Alexander von Humboldt Foundation and Klaus Tschira Stiftung. Computing resources on Blue Waters (National Center for Supercomputing Applications) and Compute Canada were used.We acknowledge Brad Gibson for reminding us to check the isotopic ratios of our models.
- Galaxy: abundances
- Physical data and processes: hydrodynamics
- Stars: abundances
- Stars: evolution
- Stars: interiors