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2005ApJ...631..540C - Astrophys. J., 631, 540-571 (2005/September-3)
Abundance anomalies and rotational evolution of low-mass red giants: a maximal mixing approach.
CHANAME J., PINSONNEAULT M. and TERNDRUP D.M.
Abstract (from CDS):
A general result of all our models is that rotational mixing, although present in small amounts, is inefficient on the lower RGB independently of any inhibiting effect of µ-barriers. Therefore, the lack of well-mixed stars before the luminosity of the RGB bump in globular clusters and the field does not constitute unquestionable evidence for the inhibition of mixing by µ-barriers. Instead, we argue that the rapid disappearance of the RGB bump as soon as mixing is allowed to penetrate µ-barriers is what actually constitutes the first solid evidence of such inhibition.
Maximal mixing models with differentially rotating envelopes are able to reproduce the 12C/13C data on M67 giants with initial rotation rates adequate to their progenitors but fail to do so for open clusters of larger turnoff mass and for metal-poor giants in the field and globular clusters. Possible solutions are discussed. Our favored scenario is one in which the overall strength of canonical extra mixing has been underestimated by existent derivations, but which additionally needs to be coupled with a much lower efficiency for rotational mixing among the rapidly rotating open cluster giants than in the slowly rotating ones in the field and globular clusters. We hypothesize that this last requirement is provided by the interaction between convection and rotation in the envelopes of giants, in the sense that rapidly rotating stars would develop much shallower angular velocity profiles in their envelopes than do slowly rotating stars.
Abstract Copyright: ∼
Journal keyword(s): Stars: Abundances - Stars: Evolution - Stars: Rotation
Simbad objects: 15
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