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 6 708 Angstrom, KI 7699 Angstrom and chromospheric H alpha lines in a group o f cool Pleiades stars. Consistent instrumentation and analysis techniques a re used to show that there is no Li I variability on time-scales of 1 year that could possibly account for the apparent spread in Li abundances seen i n Pleiades stars between effective temperatures of 4800 and 5200 K. Compari son with published data reveals tentative evidence for variability on 10-ye ar time-scales, but at a very low level. The lack of chromospheric activity variability above levels of 20 to 30 per cent 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 KI line strengths in these and published data reinforces the con clusion that it is still unsafe to attribute the Li I line strength dispers ion to a large variation in Li depletion at a given mass.