Lithium line variations in weak-lined T Tauri stars

We have observed seven weak-lined T Tauri stars to examine the effects of magnetic activity on the Li I 6707 A equivalent width and line profile. Six of the seven program stars were observed at least twice per evening on four consecutive nights. Variable Li I equivalent width is certainly present in two targets, which are the only known binaries (single-lined spectroscopic) in our sample, and likely in three others. The amplitude of the variability is consistent with previous estimates of activity effects. The variability itself supports hypotheses that observed spread in Li I equivalent widths may be explained by magnetic activity. It is unclear whether or not the binary nature of our two detections is significant. We find no indication that similarity to RS CVn systems, other than rapid rotation, is responsible for the variable activity detected. (Author)