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 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 8. [M/Fe] 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 -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.
© European Southern Observatory (ESO) 1997
Online publication: April 8, 1998