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We carry out an analysis of the Mg II 2796.34 A emission line in RS CVn starsand make a comparison with the normal stars studied in a previous paper (PaperI). The sample of RS CVn stars consists of 34 objects with known HIPPARCOSparallaxes and observed at high resolution with IUE. We confirm that RS CVnstars tend to possess wider Mg II lines than normal stars having the sameabsolute visual magnitude. However, we could not find any correlation betweenthe logarithmic line width log Wo and the absolute visual magnitude Mv (theWilson--Bappu relationship) for these active stars, contrary to the case ofnormal stars addressed in Paper I. On the contrary, we find that a strongcorrelation exists in the (Mv, log L) plane (L is the absolute flux in theline). In this plane, normal and RS CVn stars are distributed along two nearlyparallel straight lines with RS CVn stars being systematically brighter byabout 1 dex. Such a diagram provides an interesting tool to discriminate activefrom normal stars. We finally analyse the distribution of RS CVn and of normalstars in the (log L, log Wo) plane, and find a strong linear correlation fornormal stars, which can be used for distance determinations.Comment: 10 pages, 7 figures, latex, to be published in A&

A study of the Mg II 2796.34 Å emission line in late–type normal and RS CVn stars