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Evolution of Globular Cluster Stars with Mass Loss and Core Rotation

Published online by Cambridge University Press:  14 August 2015

F. Fusi-Pecci  and
A. Renzini
F. Fusi-Pecci
Affiliation:
Osservatorio Astronomico, Italy
A. Renzini
Affiliation:
Osservatorio Astronomico, Italy

Extract

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During the last decade theoretical and observational research on globular cluster stars has fairly conclusively demonstrated that the mass of horizontal-branch (HB) stars is substantially smaller (by ~ 0.2 M⊙) than the mass of their main-sequence progenitors (cf. Rood 1973, Fusi-Pecci and Renzini 1975, hereafter MPS V and FPR respectively, and the literature quoted therein). Also well established is the fact that HB stars in a single cluster do not follow a unique evolutionary path but that some dispersion in at least one HB parameter (e.g. total mass, core mass, or composition) is required. Further, a growing body of astrophysical evidence shows that the HB morphology is poorly correlated with the abundance of low-ionization potential elements (ALIPE) such as Mg, Ca, Si, and Fe. This has raised the well known problem of the “second parameter” in the sense that something else besides ALIPE has to vary from cluster to cluster, the most popular candidates being age, t, helium, Y, and CNO abundance, ZCNO. Therefore, the main problems which research on globular cluster stars is presently facing are i) a quantitative knowledge of the mass loss process, ii) the identification of the origin of the HB dispersion in a single cluster, and iii) the identification of the second parameter(s). The solution of the last point has profound implications for the theory of the early chemical and dynamical evolution the Galaxy.

Type
Part V: HR Diagrams, Horizontal Branch
Information
Symposium - International Astronomical Union , Volume 80: The HR Diagram , 1978 , pp. 225 - 228
Copyright
Copyright © Reidel 1978 

References

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