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Clarkson and Herwig 2021

Clarkson, O., and F. Herwig, 2021: Convective H-He interactions in massive population III stellar evolution models. Mon. Not. Roy. Astron. Soc., 500, no. 2, 2685-2703, doi:10.1093/mnras/staa3328.

In Pop III stellar models, convection-induced mixing between H- and He-rich burning layers can induce a burst of nuclear energy and thereby substantially alter the subsequent evolution and nucleosynthesis in the first massive stars. We investigate H-He shell and core interactions in 26 stellar evolution simulations with masses 15-140, M_☉, using five sets of mixing assumptions. In 22 cases H-He interactions induce local nuclear energy release in the range ∼10⁹-10^13.5L_☉. The luminosities on the upper end of this range amount to a substantial fraction of the layer's internal energy over a convective advection time-scale, indicating a dynamic stellar response that would violate 1D stellar evolution modelling assumptions. We distinguish four types of H-He interactions depending on the evolutionary phase and convective stability of the He-rich material. H-burning conditions during H-He interactions give ¹²C/¹³C ratios between ≈ 1.5 to ∼1000 and [C/N] ratios from ≈ -2.3 to ≈ 3 with a correlation that agrees well with observations of CEMP (carbon-enhanced metal-poor) no stars. We also explore Ca production from hot CNO breakout and find the simulations presented here likely cannot explain the observed Ca abundance in the most Ca-poor CEMP-no star. We describe the evolution leading to H-He interactions, which occur during or shortly after core-contraction phases. Three simulations without an H-He interaction are computed to Fe-core infall and a 140 M_☉ simulation becomes pair unstable. We also discuss present modelling limitations and the need for 3D hydrodynamic models to fully understand these stellar evolutionary phases.

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@article{cl02100m,
  author={Clarkson, O. and Herwig, F.},
  title={Convective H-He interactions in massive population III stellar evolution models},
  year={2021},
  journal={Monthly Notices of the Royal Astronomical Society},
  volume={500},
  number={2},
  pages={2685--2703},
  doi={10.1093/mnras/staa3328},
}

TY  - JOUR
ID  - cl02100m
AU  - Clarkson, O.
AU  - Herwig, F.
PY  - 2021
TI  - Convective H-He interactions in massive population III stellar evolution models
JA  - Mon. Not. Roy. Astron. Soc.
JO  - Monthly Notices of the Royal Astronomical Society
VL  - 500
IS  - 2
SP  - 2685
EP  - 2703
DO  - 10.1093/mnras/staa3328
ER  -

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