Effects of line-blocking on the non-LTE Fe I spectral line formation

The effects of background line opacity (line-blocking) in statistical equilibrium calculations for Fe in late-type stellar atmospheres have been investigated using an extensive and up-to-date model atom with radiative data primarily from the  Project. The background metal line opacities have been computed using data from the  stellar model atmospheres. While accounting for this line opacity is important at solar metallicity, the differences between calculations including and excluding line-blocking at low metallicity are insignificant for the non-local thermodynamic equilibrium (non-LTE) abundance corrections for Fe  lines. The line-blocking has no impact on the non-LTE effects of Fe  lines. The dominant uncertainty in Fe non-LTE calculations for metal-poor stars is still the treatment of the inelastic H  collisions, which have here been included using scaling factors to the classical Drawin formalism, and whether or not thermalisation of the high Fe  levels to Fe  ground state should be enforced. Without such thermalisation, the Fe  non-LTE abundance corrections are substantial in metal-poor stars: about 0.3 dex with efficient (i.e. Drawin-like) H  collisions and <∼ 0.5 dex without. Without both thermalisation and H  collisions, even Fe  lines show significant non-LTE effects in such stars.