Lithium abundances in classical and weak T Tauri stars

Abstract

A study on the lithium abundance in 36 T Tauri stars (mass range 0.4-2.25 M ⊙ ), partly based on high-dispersion spectra taken with the Isaac Newton Telescope, is presented. Veiling effects have been taken into account when measuring the Li I λ670.8 nm doublet equivalent width. Non-LTE effects, studied in the range 4000 ≤ T eff ≤ 5000 K, are significant for the coolest atmospheres, becoming smaller for T eff close to 5000 K. The non-LTE corrections tend to increase the derived abundance, except for high temperatures (∼ 5000 K) and log N(Li) ≥ 3, where an inverse trend is found. The majority of the stars in the sample present a rather narrow distribution of abundance around log N(Li) = 3.2, the expected value of the present cosmic lithium abundance. These results do not provide support to models of inhomogeneous big bang nucleosynthesis, that predict a very high value for the primordial lithium abudance