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

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6. Conclusions

What ever process might be responsible for producing s-process under-abundances for stars in the field with [FORMULA], is not observed to be in operation for the stars observed here. If mass loss were in operation, the [Fe/H] abundance ratios would appear higher in the RV Tau variables, than in the red giants. In fact, they are all lower in abundance, to a greater or lesser extent. If over-ionization were operating, the s-process element abundances would be lower in the RV Tau variables than in the red giants. If anything, these elements are higher in abundance. Certainly the element Sc shows no sign of depletion.

There is also no evidence that we are seeing the effects of grain deposition in any of the stars studied here. Taking RV Tau variables as a class, including all analyses from the literature, there is no evidence for a systematic s-process element under-abundance, nor for grain deposition. There is conceivably some significance in the systematic overabundances of the r-process elements Dy and Eu, and in the odd-elements Na and Al. However, a much larger sample needs to be studied before conclusions can be drawn on the systematics of the abundance ratios of the class of RV Tau variables as a whole.

Perhaps the most significant conclusion to be drawn from the present work, is that RV Tau variables are not a homogeneous class of stars at all. It seems more likely that they include stars from several different stages of evolution. The alternative, that some other parameter, like stellar mass or metallicity, has a large effect on the elemental abundances, will not explain such peculiar stars as IW Car and M56_V6.

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© European Southern Observatory (ESO) 1997

Online publication: April 8, 1998