The forbidden abundance of oxygen in the Sun

Abstract

We reexamine closely the solar photospheric line at 6300 A° , which is attributed to a forbidden line of neutral oxygen and is widely used in analyses of other late-type stars. We use a three-dimensional time-dependent hydrodynamical model solar atmosphere that has been tested successfully against observed granulation patterns and an array of absorption lines. We show that the solar line is a blend with a Ni i line, as previously suggested but oftentimes neglected. Thanks to accurate atomic data on the [O i] and Ni i lines, we are able to derive an accurate oxygen abundance for the Sun: log e(O) = 8.69 ± 0.05 dex, a value at the lower end of the distribution of previously published abundances but in good agreement with estimates for the local interstellar medium and hot stars in the solar neighborhood. We conclude by discussing the implication of the Ni i blend on oxygen abundances derived from [O i] λ6300 in disk and halo stars.