ar X iv : a st ro - p h / 98 08 17 8 v 1 1 8 A ug 1 99 8 New clues on non - standard mixing on the RGB 1
نویسندگان
چکیده
It has been known for a long time that low mass red giants (i.e., with initial mass lower than ∼ 2 M⊙) present chemical anomalies which are not predicted by the standard evolution theory. In particular, the models which neglect the transport of chemicals in the stellar radiative regions can not explain the observed behavior of the carbon isotopic ratio both in Pop I and II stars on the red giant branch (RGB), of the lithium and carbon abundances (respectively in halo and globular cluster giants) after the completion of the first dredge-up, neither the evidences of O versus N anticorrelation and Na and Al versus N correlation seen in a large number of globular cluster giants (see Charbonnel, Brown & Wallerstein 1998, hereafter CBW98, for references). These observations suggest that low mass stars undergo a non-standard mixing process which adds to the first dredge-up and modifies the surface abundances.
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