A DIP IN THE CAII H-EMISSION-LINE AND K-EMISSION-LINE FLUXES FOR HYADES F-STARS

The Hyades chromospheric emission line fluxes for the Ca H and It line s show a minimum at B-V = 0.45, very close to the minimum for the Li s urface abundances. No anomalies have been reported for Ca surface abun dances in Hyades F stars, though published abundance analyses may have missed stars at this B-V. We do, therefore not think that the dip in the CaII emission is due to diffusion (as believed to be the case for Li) but rather suspect that it is a chromospheric effect. Only on the branch of the dip with declining fluxes for increasing B-V (which mean s for B-V = 0.43 and 0.44) a correlation of the CaII emission with v s ini is seen.