LITHIUM IN RS-CANUM-VENATICORUM BINARIES AND RELATED CHROMOSPHERICALLY ACTIVE STARS .3. NORTHERN RS-CVN SYSTEMS

High-resolution spectra of Northern RS CVn binaries obtained at the NS O-KittPeak are analyzed with a spectrum synthesis code to derive Li ab undances, metallicities and rotation rates. The data are then combined with previous observations of Southern RS CVn binaries obtained at ES O, yielding a total sample of 67 individual components in 54 catalogue d RS CVn binaries. We confirm the presence of substantial amounts of L i in many chromospherically active stars in the sample, with no signif icant difference between the Northern and Southern samples. We specifi cally address the question of whether these relatively high Li abundan ces are due to enhanced chromospheric activity or rather are a consequ ence of evolutionary history in stars of sufficiently high mass. We in vestigate the dependence of Li abundance on mass by using mass determi nations in binary systems as well as comparison with theoretical evolu tionary tracks. We show that while Li abundances in subgiants and in t he warmer stars of the sample may be consistent with a dependence on m ass, there is no clear indication in the data that the cooler giants w ith larger Li abundances are also the more massive ones. Uncertainties in the comparison with evolutionary tracks may partially be responsib le for this negative result. Alternatively, Li depletion and dilution in evolved stars may be more complex than predicted by standard evolut ionary models.