The effect of stellar activity on the Li I 6708, Na I 5896 and K I 7699 Ålines - A comparison with the Pleiades, field stars and the Sun

An analytical model has been developed to empirically study the eects of stellar spots and faculae on the observed equivalent widths of Li i 6708, Na i 5896 and K i 7699 A lines (and abundances in the case of lithium) in late-type stars, taking into account the changes in the observed magnitudes and colors. Solar spectra corresponding to dierent active regions are used as input data and a range of lling factors are applied to simulate the surfaces of stars with dierent levels of activity. Detailed comparisons between predicted and observed photometric colors and equivalent widths are made for late-type stars of the Pleiades and the eld. The observed dispersions in K i and Li i equivalent widths for Pleiades stars can be partially accounted by the simultaneous eects of activity on colors and the line formation, indicating that the lithium-rotation connection suggested for0:7 0:9 M Pleiades stars could be due in part to the stellar activity. However, under realistic values for the lling factors, only a small portion of the observed spread could be explained by these eects.