Publication Abstracts

Stothers and Chin 1996

Stothers, R.B., and C.-W. Chin, 1996: Metal dependencies of two convection theories for cool stellar envelopes. Astrophys. J., 469, 166-170, doi:10.1086/177768.

Most theories of turbulent convection in stellar envelopes assume incompressible flow, and so require the assignment of a characteristic length scale from external evidence. In mixing-length theory, this length l is usually assigned to be a constant, α, times the local pressure scale height, HP, or, alternatively, times the distance from the top of the convection zone, z. The new full-spectrum-of-turbulence theory of Canuto & Mazzitelli uses l = z, and therefore is formally parameter-free. Chieffi, Straniero, & Salairis have recently suggested that α in mixing-length theory depends on metallicity, Z, but they considered only low-mass stars. We do a similar analysis for stars of higher mass. Specifically, we compare predicted and observed effective temperatures of red giants and red supergiants of widely differing metallicities, but identical luminosities, within the mass range 5-10 M. The stars utilized belong to several open clusters in the Galaxy with Z — 0.02 and to the clusters NGC 330 and NGC 458 in the Small Magellanic Cloud with Z = 0.002-0.004. It appears that either α in mixing-length theory is independent of metallicity or, since the empirical effective temperatures os the SMC stars have been underestimated, α increases slightly with decreasing metallicity. On the other hand, Canuto & Mazzitelli's theory with l = z is found to perform quite well in all cases, within the possible errors of the observations and of the low-temperature opacities.

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BibTeX Citation

  author={Stothers, R. B. and Chin, C.-W.},
  title={Metal dependencies of two convection theories for cool stellar envelopes},
  journal={Astrophys. J.},

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RIS Citation

ID  - st09700z
AU  - Stothers, R. B.
AU  - Chin, C.-W.
PY  - 1996
TI  - Metal dependencies of two convection theories for cool stellar envelopes
JA  - Astrophys. J.
VL  - 469
SP  - 166
EP  - 170
DO  - 10.1086/177768
ER  -

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