2008ApJ...689.1279P

We address the evolution of lithium in Population II dwarf stars under the joint effects of microscopic diffusion and tachocline mixing. This process relies on analytical developments and is also constrained by helioseismology observations. It was successfully applied to solar analogs but never investigated in halo stars. It is induced in the upper radiation zone by rotation and a slight differential rotation in latitude. Consequently we modeled different possible rotation histories of halo stars, showing that the initial rotation rate had no impact on lithium in the framework of tachocline mixing. We find a negligible impact of pre-main-sequence evolution on ^ 7^Li independent of metallicity provided that [Fe/H]←1. On the contrary, microscopic diffusion and tachocline turbulence act on the long term of main sequence and shape the current ⁷Li-T_eff pattern from the turnoff down to 5000 K. The tachocline mixing models fit the ⁷Li-T_eff relation better than the pure microscopic diffusion models. We address the issue of warm ⁷Li-poor stars and conclude that a moderate mass transfer from a companion could explain their composition. Finally, we discuss the lithium lighter isotope. The pre-main-sequence and main-sequence ^ 6^Li depletion we compute seems difficult to reconcile with the current observations.