Lithium abundances in dwarfs of intermediate age open clusters

Abstract

Lithium abundance measurements in dwarf stars in open clusters are of crucial importance for our understanding of the mixing mechanism and have allowed us to achieve important conclusions on the matter. However, in order to further our understanding of what drives lithium depletion, lithium abundance measurements have to be coupled with accurate temperature determinations, which are best achieved when the analysis of iron lines is employed. Effective temperature estimations from photometry, on the contrary, can be affected by errors as large as several hundred kelvins due to uncertain open cluster reddening, especially when studying old open clusters, which tend to be more distant. We present lithium abundance in 12 dwarfs belonging to 4 open clusters at about 1 or 2 Gyr. The stellar effective temperatures, along with the other parameters, were estimated from the analysis of about 60 Fe I lines and 10 Fe II. Even though the few datapoints call for caution, we notice that stars in the open cluster IC 4651 seem to present a steep decline with temperature below 6000 K.