Fernández Figueroa, María JoséSedano, J. L.Castro Rubio, Elisa De2023-06-212023-06-211986-110004-6361https://hdl.handle.net/20.500.14352/64986© European Southern Observatory. The authors are very grateful to Dr. F.M. Walter for many valuable comments and suggestions.We have studied a sample of ten RS CVn systems by means of IUE high resolution long wavelength spectra. A general trend toward decreasing chromospheric activity (R_hk) for slower rotating stars has been found. Considering the R_hk values and their relation with structural parameters (T_eff, logg, log P_rot) we suggest that there are two pos­sible different activity levels. The less active systems have Rhk chromospheric activity levels similar to the single cool stars showing the same general trend. A relation between R_hk and the inverse Rossby number has been obtained, in which the RS CVn stars fill the gap found by Rucinski between W UMa and the main-sequence stars.engjournal articlehttp://adsabs.harvard.edu/abs/1986A%26A...169..237Fhttp://www.aanda.org/open access52RS CVn binariesChromospheric activityMg II emissionAstrofísicaAstronomía (Física)