The Wilson-Bappu effect of the MgII k line - dependence on stellar temperature, activity and metallicity
Oystein Elgaroy 1,
Oddbjorn Engvold 1 and
Niels Lund 2
Received 1 October 1997 / Accepted 10 March 1998
The Wilson-Bappu effect is investigated using accurate absolute magnitudes of 65 stars obtained through early release of data from the Hipparcos satellite together with MgII k line widths determined from high resolution spectra observed with the International Ultraviolet Explorer (IUE) observatory.
Stars of spectral classes F, G, K and M and luminosity classes I-V are represented in the sample. Wilson-Bappu relations for the Mg II k line for stars of different temperatures i.e. spectral classes are determined. The relation varies with spectral class and there is a significant scatter of the line 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 and stellar activity. A difference in behavior between dwarfs and giants (and supergiants) of spectral class K seems to be present. Magnetic activity affects the width of the Mg II k line in dwarfs. Metallicity is found to influence the Mg II k line width in giants and supergiants. Possible interpretations of the new results are briefly discussed.
Key words: stars: activity stars: chromospheres
Send offprint requests to: O. Engvold (e-mail: firstname.lastname@example.org)
© European Southern Observatory (ESO) 1999
Online publication: March 1, 1999