First results from hydrodynamic simulations of convective-reactive proton-C12 combustion in the He-shell flash of Sakurai's object [SSA]

The mixing of proton-rich material into C12-rich He-shell flash convection induces exotic n-capture nucleosynthtesis and is encountered in the late phases of the evolution of different types of stars. Examples include the first generations of low- and intermediate mass and massive stars that formed in the early universe. The He-shell flash convection during the post-AGB evolution provides a solar-like metallicity example of a H-ingestion event that can validate multi-physics simulations. Previously we have demonstrated that light curve and abundance observations of post-AGB star Sakurai’s object can only be reproduced by stellar evolution simulations if mixing-length theory mixing properties are modified. Our initial 3D simulations of the entrainment and burning of protons into the He-shell flash convection zone confirm some properties of stellar evolution models and identify aspects that are not correctly described in 1D models. 3D and 1D simulations aggree in that a H-burning driven convection zone emerges inside the original He-shell flash convection zone after a relatively short time after the H-ingestion starts, in terms of the entrained mass of protons. The location of the H-burning convection zone in the 3D simulation only agrees with a 1D model in which the mixing efficiency is calibrated to reproduce the light curve. Unlike stellar evolution predictions we have no evidence in 3D hydrodynamic simulations for the formation of a strict mixing split between the two convection zones up to the end of our present simulations at ~ 10hr, consistent with our previous analysis of nucleosynthesis constraints.

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Date added: Fri, 18 Oct 13