THE 777 NM OXYGEN TRIPLET IN THE SUN AND SOLAR-TYPE STARS, AND ITS USE FOR ABUNDANCE ANALYSIS

The use of the neutral oxygen triplet lines at 777 nm and other atomic lines for abundance analysis of the Sun and solar-type stars is investigated and discussed taking into account the effects on these lines by departures from local thermodynamic equilibrium (NLTE effects). It is found that the discrepant behaviour of the 777 nm triplet in the Sun is not possible to explain within the context of one-dimensional homogeneous model atmospheres. It seems very likely that the inhomogeneous properties of the solar photosphere (granulation) must be taken into account to reproduce these lines with the accuracy needed for precision abundance analyses. Experiments with line calculations in a solar granulation simulation snapshot are made, leading to one possible mechanism for the suppression of the NLTE effect that is predicted for the 777 nm triplet lines by one-dimensional model atmospheres.