A Low Solar Oxygen Abundance from the First‐Overtone OH Lines

Abstract

An extremely high resolution (>105) high signal-to-noise ratio (>103) solar spectrum has been used to measure 15 very weak first-overtone (Δv = 2) infrared OH lines, resulting in a low solar abundance of AO ≈ 8.6 when MARCS, three-dimensional, and spatially and temporally averaged three-dimensional model atmospheres are used. A higher abundance is obtained with Kurucz (AO ≈ 8.7) and Holweger & Müller (AO ≈ 8.8) model atmospheres. The low solar oxygen abundance obtained in this work is in good agreement with a recent three-dimensional analysis of [O I], O I, OH fundamental (Δv = 1) vibration-rotation, and OH pure rotation lines. The present result gives further support for a low solar metallicity, and although using a low solar abundance with OPAL opacities ruins the agreement between the calculated and the helioseismic measurement of the depth of the solar convection zone, recent results from the Opacity Project show that the opacities near the base of the solar convection zone are larger than previously thought, lending further confidence to a low solar oxygen abundance.