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Astron. Astrophys. 343, 222-228 (1999)

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4. Conclusions

Early release of data from the Hipparcos satellite has served to provide accurate absolute magnitudes for 65 stars for which the Mg II k line widths have been measured from high resolution spectra obtained with the International Ultraviolet Explorer (IUE) observatory.

Increased accuracy and knowledge of the uncertainty in the values of the absolute magnitudes has permitted new features of the Wilson-Bappu effect to be explored. Firstly, we have established that the scatter of the data around the regression line found by Elgaroy et al. (1997) is real, and not due to errors. Secondly, a differentiation of the material according to surface temperature has been possible, and the Wilson-Bappu relations for stars of spectral classes F, G, K, and M have been determined. Thirdly, it has been noticed ed that the line width of K giants decreases with activity for [FORMULA]0.02 (i.e. for the broadest cases), whereas the widths increase with activity for K dwarfs. Correlation between deviation from average line width and metallicity for K giants is suggested. However, K dwarfs do not show a similar relation, very likely because the effect of magnetic activity then is dominating.

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© European Southern Observatory (ESO) 1999

Online publication: March 1, 1999