LITHIUM ISOTOPES IN POPULATION II DWARFS

作者：Piau L^*

来源：Astrophysical Journal, 2008, 689(2): 1279-1288.

DOI：10.1086/592722

• Galaxy: halo
• stars: abundances
• stars: interiors
• stars: Population II
• stars: rotation

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 preYmain-sequence evolution on Li-7 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 Li-7-T-eff pattern from the turnoff down to 5000 K. The tachocline mixing models fit the Li-7-T-eff relation better than the pure microscopic diffusion models. We address the issue of warm Li-7-poor stars and conclude that a moderate mass transfer from a companion could explain their composition. Finally, we discuss the lithium lighter isotope. The preYmain-sequence and main-sequence Li-6 depletion we compute seems difficult to reconcile with the current observations.

• 出版日期2008-12-20
• 单位中国地震局