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Astron. Astrophys. 326, 1069-1075 (1997)

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5. RV Tau variables as a class

It is important to consider whether we can say anything new about the systematic characteristics of the elemental abundances of RV Tau variables as a class. In Table 8 the solar differential abundances are listed for all the stars studied here, and in the literature. In deriving the mean for RV Tau variables as a class, equal weight was given to the mean of the five stars in Luck & Bond (1989), and to IW Car plus the three stars from this work. The results are shown graphically in Fig. 6. Here the error bars of [FORMULA] 0.3dex, are for illustrative purposes only. The set of stars is so disparate and small, that it is meaningless to attempt calculating more representative errors. Nevertheless, 0.3dex should be considered conservative.

[TABLE]

Table 8. [M/Fe] for RV Tau variables as a class

[FIGURE] Fig. 6. Mean metal to Fe ratios, relative to solar, for RV Tau variables as a class

From Fig. 6 we see that there is no evidence for a systematic underabundance in the s-process elements. The only element falling significantly below zero is Pr, and as this is poorly determined, it is not considered significant. Interestingly, Eu and Dy are the only two n-capture elements that appear slightly over-abundant. While Dy is poorly determined, Eu is somewhat more reliable. Both elements are mainly r-process in origin, rather than s-process. However, Sm is thought to be 70% r-process in origin (Gratton & Sneden, 1994), and does not share the over-abundance of the two heavier elements.

At the other end of the scale, both odd elements Na and Al are significantly over-abundant, indicating 3rd dredge-up contamination. The [FORMULA] -elements Mg, Si, S and Ti1 are all enhanced, while Ca is not at all. Again, this could be evidence for dredge-up of processed material.

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© European Southern Observatory (ESO) 1997

Online publication: April 8, 1998
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