The non-synchronous systems among RS CVN stars

An RS CVn star is considered as non-synchronous if its orbital period differs by more than 4% from its photometric period. Of 88 systems examined according to this criterion, 67 are synchronous, 21 are non-synchronous. For the 21 non-synchronous systems, we find their spectral types are most around KO-2 III, that their orbital eccentricities are larger and their chromospheric activity lower than the average level.