Publication Abstracts

Stothers and Chin 1976

Stothers, R., and C.-W. Chin, 1976: Stellar evolution at high mass with semiconvective mixing according to the Schwarzschild criterion. Astrophys. J., 204, 472-480, doi:10.1086/154191.

New evolutionary sequences of models for stars of 5-60 M with four different initial chemical compositions have been constructed with the use of the Schwarzschild criterion for convection. This criterion leads to semiconvection outside the convective core (1) just after the zero-age mainsequence stage for masses greater than ∼12 M and (2) just before the stage of central hydrogen exhaustion for masses greater than ∼6 M. The base of the semiconvective zone thereafter becomes fully convective, with the result that the hydrogen profile in the intermediate zone acquires a local plateau. Competition between the effects of the hydrogen plateau, of the envelope opacity, and of the luminosity-to-mass ratio provides the reason why the post-main-sequence evolutionary tracks on the H-R diagram are found to vary widely as a function of initial chemical composition for masses less than ∼17 M and why, for higher masses, the tracks invariably reach the red region of the H-R diagram only toward the end of core helium burning. The tracks for the more massive stars are found to be relatively insensitive to the uncertainties in the nuclear reaction rates. Small differences among the sequences computed by different authors are probably due mostly to slight differences in the opacities adopted. It is found that the rather cool range of effective temperatures predicted for stable blue supergiants with masses above ∼20 M is not in agreement with the observations. An observational test utilizing the surface hydrogen abundance of stellar remnants in binary systems is at present inconclusive in deciding whether the Schwarzschild criterion or the Ledoux criterion is the correct criterion for convection to use. It is strongly suggested that neither criterion with any reasonable adopted initial chemical composition can at present lead to model predictions that satisfy all the observational requirements.

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BibTeX Citation

  author={Stothers, R. and Chin, C.-W.},
  title={Stellar evolution at high mass with semiconvective mixing according to the Schwarzschild criterion},
  journal={Astrophys. J.},

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RIS Citation

ID  - st02610g
AU  - Stothers, R.
AU  - Chin, C.-W.
PY  - 1976
TI  - Stellar evolution at high mass with semiconvective mixing according to the Schwarzschild criterion
JA  - Astrophys. J.
VL  - 204
SP  - 472
EP  - 480
DO  - 10.1086/154191
ER  -

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