Formation of L[CLC]i[/CLC] [CSC]i[/CSC] Lines in Photospheric Granulation

Abstract

The possibility of significant systematic errors due to the use of one-dimensional homogeneous atmospheres in lithium-abundance determinations of cool stars motivates a study of non-local thermodynamic equilibrium (NLTE) effects on Li I line formation in a three-dimensional solar granulation simulation snapshot. The NLTE effect on the equivalent width of the 671 nm resonance line is small in one-dimensional models or in integrated light from the granulation model. The line-strength variations over the granulation pattern are, however, markedly different in NLTE compared with LTE—observations of this may provide diagnostics to NLTE effects. The effects of horizontal photon exchange found in the granulation model are moderate and due entirely to bound-bound processes; ultraviolet overionization is unimportant.