Heating and cooling by iron in cool star winds

The role of iron for the energy balance in the extended atmospheres and cir cumstellar envelopes of cool stars is explored. Based on large non-LTE mode l atoms for Fe I and FeII, we study the influence of fine-structure, forbid den, permitted and bound-free transitions on the radiative heating and cool ing of the gas under various temperature, density and radiation field condi tions. The results are compared to those obtained in LTE and to those calcu lated when ignoring optical depth effects in the lines. The number of level s in the model atoms necessary to achieve convergence of the results is dis cussed.