Publication Abstracts

Stothers and Chin 1975

Stothers, R., and C.-W. Chin, 1975: Stellar evolution at high mass with semiconvective mixing according to the Ledoux criterion. Astrophys. J., 198, 407-417, doi:10.1086/153615.

Semiconvective mixing has been included in new evolutionary sequences of models for stars of 10, 15, and 30 M☉, with four different initial chemical compositions. The models have been constructed with the help of the Ledoux criterion both for the definition of convective instability and for the state of convective neutrality that is assumed to be attained in regions with a gradient of mean molecular weight. Allowance for convective overshooting has also been made. Semiconvection is found to be almost nonexistent at 10 M☉ and of minor importance at 15 M☉. But at 30 M☉, semiconvection covers most of the intermediate zone and develops into full convection if the initial hydrogen and metals abundances are both high. If the initial metal abundance is low, a "blue loop" phase follows the early red-supergiant phase during core helium burning, just as it does for all initial chemical compositions at 10 and 15 M☉, when the new 3α reaction rate is adopted. If the initial hydrogen abundance is low, the star goes directly into a "blue hook" phase without first becoming a red supergiant. The critical importance of the depths of the semiconvective zone and of the outer convective envelope in promoting a blue loop and in determining the maximum effective temperature attained on the loop is demonstrated. The thermally stable stages of the blue-loop phase cover an amount of log Te and a fraction of the helium-burning lifetime that are almost independent of stellar mass, although the maximum effective temperature attained on the loop is hotter at higher stellar masses. The effective temperature ranges agree roughly with observational data, but the predicted blue-to-red ratios for masses higher than about 15 M☉ do not.

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BibTeX Citation

@article{st09010c,
  author={Stothers, R. and Chin, C.-W.},
  title={Stellar evolution at high mass with semiconvective mixing according to the Ledoux criterion},
  year={1975},
  journal={Astrophysical Journal},
  volume={198},
  pages={407--417},
  doi={10.1086/153615},
}

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RIS Citation

TY  - JOUR
ID  - st09010c
AU  - Stothers, R.
AU  - Chin, C.-W.
PY  - 1975
TI  - Stellar evolution at high mass with semiconvective mixing according to the Ledoux criterion
JA  - Astrophys. J.
JO  - Astrophysical Journal
VL  - 198
SP  - 407
EP  - 417
DO  - 10.1086/153615
ER  -

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