Result of the principal component analysis (PCA). Top plot: the data plotted along the first and second principal components. Objects with detected line asymmetries are plotted with filled circles, their shade corresponds to the measured event rate. Bottom plot: the coefficients for the first three principal components (PCs). The main features of the first PC are related mainly to stellar structure, while the features in the second PC are mainly related to EUV and X-ray activity indices.