出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：The He-shell flash convection in AGB stars is the site for the high-temperature component of
the s-process in low- and intermediate mass giants, driven by the 22Ne neutron source. During
this phase several s-process branchings are activated, including some with time scales similar
to the convective turn-over time scale. In addition, uncertainties regarding convective mixing
at both the bottom and the top of the convective shell are preventing accurate predictions of sprocess
yields. The upper convection boundary plays a critical role during the H-ingestion episode
that may lead to neutron-bursts in the most metal-poor AGB stars. We address these problems
through global 3-dimensional hydrodynamic simulations including the entire spherical He-shell
flash convection zone (as oposed to the 3D box-in-a-star simulations). An important aspect of
our current effort is to establish the feasibility of our appoach. We explain why we favour the
explicit treatment over the anelastic approximation for this problem. The simulations presented
in this paper use a Cartesian grid of 5123 cells and have been run on four 8-core workstations for
four days to simulate 5000s, which corresponds to almost ten convective turn-over times. The
convection layer extends radially at the simulated point in the flash evolution over 7Hp pressure
scale-heights and exceeds the size of the underlying core. Convection is dominated by large
convective cells that fill more than an entire octant. In order to better understand the conditions
of the s-process branchings in this environment we have extracted particle tracers, and we discuss
the thermodynamic trajectories along those paths.
