On the dispersion in lithium and potassium among late-type stars in young clusters: IC

We have measured the equivalent width (EW) of the K i 7699 Å line in a sample of G and K–type members of the ∼ 35 Myr old cluster IC 2602 for which a dispersion in Li EWs had been reported by previous studies. Active cluster stars with 0.75 <∼ B−V0 <∼ 1 are characterized by a dispersion in the EW of the K i 7699 Å, while earlier and later–type stars do not show any significant scatter. Cluster stars at all colors show potassium EW excesses with respect to field inactive stars; furthermore, a statistically significant relationship is found between differential potassium EWs and log LX/Lbol ratios, indicating that the EWs of the potassium feature are altered by activity. Our results suggest that the dispersion in Li EWs observed among cluster stars later than B−V0 ∼ 1 cannot be fully explained by the effects of activity. No final conclusion can instead be drawn for earlier–type stars.