On the lithium abundance dispersion in late-type Pleiades stars

I present the results of a programme to monitor the strengths of the Li I 6708A, K I 7699A and chromospheric Halpha lines in a group of cool Pleiades stars. Consistent instrumentation and analysis techniques are used to show that there is no Li I variability on timescales of 1 year that could possibly account for the apparent spread in Li abundances seen in Pleiades stars between effective temperatures of 4800-5200K. Comparison with published data reveals tentative evidence for variability on 10 year timescales, but at a very low level. The lack of chromospheric activity variability above levels of 20 to 30 percent makes it difficult however, to rule out evenly distributed magnetic activity regions causing a scatter in the Li I line strengths at a given abundance. The similar star to star scatter of K I line strengths in these and published data reinforces the conclusion that it is still unsafe to attribute the Li I line strength dispersion to a large variation in Li depletion at a given mass.