Publication Abstracts

Stothers 1991

Stothers, R.B., 1991: Observational tests of convective core overshooting in stars of intermediate to high mass in the Galaxy. Astrophys. J., 383, 820-836, doi:10.1086/170840.

Fourteen tests for the presence of convective overshooting in large convecting stellar cores are discussed for stars with masses of 4-17 M which are members of detached close binary systems and of open clusters in the Galaxy. Nine of these tests, including all the best tests, are either new or newly applied. A large amount of theoretical and observational data has been scrutinized and subjected to averaging in order to minimize accidental and systematic errors. Defining a ratio of the effective convective overshoot distance beyond the classical Schwarzschild core boundary to the local pressure scale height, the present investigation finds a conservative upper limit of d/Hp < 0.4 from at least four tests and a tighter upper limit of d/Hp < 0.2 from one good test that is subject to only mild restrictions and is based on the maximum observed effective temperature of evolved blue supergiants. All the best test results, however, are formally consistent with the assumption of d/Hp = 0 and are not sensitive to uncertainties about the initial chemical composition (or, probably, the opacities). Further analysis shows why the values of d/Hp = 0.25-2 that were derived in previous studies should probably be regarded as only upper limits.

Three additional conclusions can be drawn specifically concerning the B-type main-sequence stars. First, any current uncertainty about the distance scale for these stars is unimportant in conducting the present tests for convective core overshooting. Second, the correct effective temperature scale for the B0.5-B2 stars is almost certainly close to one of the proposed hot scales. Third, the value of the inital metals abundance that is required in stellar models in order to reproduce the observations is Ze ≈ 0.04 independently of overshooting; this exceptionally high value, which is twice the directly observed atmospheric metals abundance in most of these stars, may indicate the need for larger envelope opacities than the standard Los Alamos opacities used here.

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BibTeX Citation

@article{st04600x,
  author={Stothers, R. B.},
  title={Observational tests of convective core overshooting in stars of intermediate to high mass in the Galaxy},
  year={1991},
  journal={Astrophys. J.},
  volume={383},
  pages={820--836},
  doi={10.1086/170840},
}

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RIS Citation

TY  - JOUR
ID  - st04600x
AU  - Stothers, R. B.
PY  - 1991
TI  - Observational tests of convective core overshooting in stars of intermediate to high mass in the Galaxy
JA  - Astrophys. J.
VL  - 383
SP  - 820
EP  - 836
DO  - 10.1086/170840
ER  -

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