6 Conclusions

The high-resolution optical spectra of the two X-ray active binaries RS CVn stars HD 113816 (IS Vir) and HD 119285 (V851 Cen) have been analysed, using three different techniques. The techniques have been compared in order to establish their respective merits and drawbacks. The present results show that the Fe  I low excitation potential transitions do not appear significantly affected by non-LTE effects, and, as a consequence, the iron excitation equilibrium is a reliable diagnostic in the two studied RS CVn. At the same time, the V-I photometric index gives significantly colder (and by comparison with the other approaches, likely underestimated) effective temperatures than the B-V index.

Both IS Vir and V851 Cen are found to be near-solar metallicity giants, with the latter somewhat underabundant in Fe (but significantly more metal rich, for V851 Cen, than found by Randich et al. 1994). Both stars present overabundances with respect to the solar pattern of their Na, Mg, Al and Ca to Fe ratios. In addition IS Vir exhibits a modest underabundance in Ni, while V851 Cen shows overabundances of Si, Sc and Ti. The analysis of a large sample will be interesting to see whether this apparent peculiar abundance pattern is a general characteristic of active binaries.

Acknowledgements

We are very grateful to R. Kurucz, C. Sneden and the VALD people for making their software packages and atomic and molecular data available to the community. We would like to thank F. Arenou, B. Barbuy, V. Hill, M. Spite, F. Spite, C. van 't Veer, I. Pillitteri and J. Drake for the very fruitful discussions and advice.