RT Journal Article T1 The Mg II emission in a sample of regular-period RS CVn systems A1 Fernández Figueroa, María José A1 Sedano, J. L. A1 Castro Rubio, Elisa De AB 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. PB EDP Sciencies SN 0004-6361 YR 1986 FD 1986-11 LK https://hdl.handle.net/20.500.14352/64986 UL https://hdl.handle.net/20.500.14352/64986 LA eng NO © European Southern Observatory. The authors are very grateful to Dr. F.M. Walter for many valuable comments and suggestions. DS Docta Complutense RD 8 abr 2025