The Solar Oxygen Abundance from an Empirical Three-Dimensional Model

The Oxygen abundance in the solar photosphere, and consequently the solar metallicity itself, is still a controversial issue with far-reaching implications in many areas of Astrophysics. This paper presents a new determination obtained by fitting the forbidden OI line at 6300 A with an observational 3D model. The approach presented here is novel because previous determinations were based either on 1D empirical stratifications or on 3D theoretical models. The resulting best-fit abundances are lg E(O)=8.90 and lg E(Ni)=6.15. Nevertheless, introducing minor tweaks in the model and the procedure, it is possible to retrieve very different values, even down to lg E(O)=8.70. This extreme sensitivity of the abundance to possible systematic effects is not something specific to this particular work but probably reflects the real uncertainty inherent to all abundance determinations based on a prescribed model atmosphere.