The Wilson-Bappu effect of the MgII k line - dependence on stellar temperature, activity and metallicity

The Wilson-Bappu effect is investigated using accurate absolute magnitudes of 65 stars obtained through early release of data from the Hipparcos satel lite together with MgII k fine widths determined from high resolution spect ra observed with the International Ultraviolet Explorer (IUE) observatory. Stars of spectral classes F, G, K and M and luminosity classes I-V are repr esented in the sample. Wilson-Bappu relations for the Mg II k line for star s of different temperatures i.e. spectral classes are determined. The relat ion varies with spectral class and there is a significant scatter of the li ne widths around the regression lines. The sample contains slowly rotating stars of different activity levels and is suitable for investigations of a possible relation between line width an d stellar activity. A difference in behavior between dwarfs and giants (and supergiants) of spectral class K seems to be present. Magnetic activity af fects the width of the Mg II k line in dwarfs. Metallicity is found to infl uence the Mg II k line width in giants and supergiants. Possible interpreta tions of the new results are briefly discussed.