Speaker
Ondrea Clarkson
(University of Victoria)
Description
Interactions between H- and He-shell convection layers have been seen in 1D stellar models of massive Pop III stars \cite{WW,LC} but until recently have not been investigated in detail. Using the 1D stellar evolution code \texttt{MESA}, we find that when this event occurs in a 45 \,\mathrm{M_Pop III model, it leads to H-burning luminosities of $\mathrm{\log L_HL_sim13$ due to convective-reactive mixing at the interface between the two shells. These conditions render 1D models unreliable and we will report on initial results of our new project to investigate the hydrodynamic nature of mixing at the interface between the H- and He-convection zone (Fig.\,1).
This mixing is similar to H-ingestion events found in other environments, such as He-shell flashes in low-mass stars \cite{FH1,FH2} and may lead to the \textit{i}-process with neutron densities of $\approx 10^{13} \mathrm{cm}^{-3}$, reproducing the nucleosynthetic abundance patterns (Fig.\,2) existing in some of the most metal-poor stars \cite{PopIII-ip}. We have now also investigated in more detail the conditions for Ca production in Pop III stars, and specifically the role of the 19\mathrm{F}(p,\gamma)^{20}\mathrm{Ne}$ reaction. Using default rates, we find that unless mixing between H-and He layers is involved Ca is produced at a level at least a factor 10 below the value observed in the most Fe-poor star.
Primary author
Ondrea Clarkson
(University of Victoria)
Co-authors
Falk Herwig
(University of Victoria)
Huaqing Mao
(University of Minnesota)
Marco Pignatari
(University of Hull)
Paul Woodward
(University of Minnesota)
Robert Andrassy
(University of Victoria)
