lithium depletion boundary (LDB)
Lithium depletion boundary (LDB) is a new age-dating method proposed for open clusters based on determination of the lithium abundances of cluster members whose masses are near the hydrogen burning mass limit. The idea behind this method is that for stars near the substellar mass limit, the age at which stars become hot enough in their cores to burn lithium is a sensitive function of mass. Furthermore, it is argued that the physics required to predict the location of the LDB as a function of age is well understood and not subject to much uncertainty. In the mass range of interest, stars are fully convective, and the core lithium abundance will be directly reflected in the surface lithium abundance, which can be determined from measurements of the 6708 Å Li I doublet.