Publication Abstracts
Stothers and Chin 1992
, and C.-W. Chin, 1992: Stellar evolution in blue populous clusters of the Small Magellanic Cloud and the problems of envelope semiconvection and convective core overshooting. Astrophys. J., 390, 136-143, doi:10.1086/171266.
Two of the blue populous clusters in the Small Magellanic Cloud, NGC 330 and NGC 458, contain a considerably larger number of evolved stars than are found in comparably young clusters in our Galaxy. This richness makes them valuable tools for studying post-main-sequence evolution in the mass range 4-15 M☉. Accordingly, new theoretical evolutionary sequences of models for stars with low metallicities, appropriate to the Small Magellanic Cloud, are derived here with both standard Cox-Stewart opacities and the new Rogers-Iglesias opacities. We find that only those sequences with little or no convective core overshooting can reproduce the two most critical observations: the maximum effective temperature displayed by the hot evolved stars and the difference between the average bolometric magnitudes of the hot and cool evolved stars. An upper limit to the ratio of the mean overshoot distance beyond the classical Schwarzschild core boundary to the local pressure scale height can be set at d/Hp < 0.2. Although the use of the maximum effective temperature is subject to certain mild restrictions, the bolometric magnitude difference is an ideal quanitity, being sensitive only to the stellar core mass. A second important result derived here from the frequency of cool supergiants in NGC 330 is that the Ledoux criterion (rather than the Schwarzschild criterion) for convection and semi-convection in the envelopes of massive stars is strongly favored. Both conclusions are independent of current uncertainties about the adopted stellar metallicities and the radiative opacities. However, the Rogers-Iglesias opacities produce superior model fits to other observational quantities. Residuals from the fitting for NGC 330 suggest the possibility of fast interior rotation in the stars of this cluster. NGC 330 and NGC 458 turn out to have ages ∼3×107 yr and ∼1×107 yr, respectively.
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BibTeX Citation
@article{st06600q,
author={Stothers, R. B. and Chin, C.-W.},
title={Stellar evolution in blue populous clusters of the Small Magellanic Cloud and the problems of envelope semiconvection and convective core overshooting},
year={1992},
journal={Astrophysical Journal},
volume={390},
pages={136--143},
doi={10.1086/171266},
}
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RIS Citation
TY - JOUR ID - st06600q AU - Stothers, R. B. AU - Chin, C.-W. PY - 1992 TI - Stellar evolution in blue populous clusters of the Small Magellanic Cloud and the problems of envelope semiconvection and convective core overshooting JA - Astrophys. J. JO - Astrophysical Journal VL - 390 SP - 136 EP - 143 DO - 10.1086/171266 ER -
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