Chemical Evolution of the Orion Association. IV. The Oxygen and Iron Abundances of F and G Stars

Abstract
Oxygen and iron abundances are derived for a sample of pre-main-sequence F and G stars of the Orion association. Results for association members are compared with results published previously for main-sequence B stars in the association. The abundances reveal that the F and G stars exhibit the pattern of abundances shown by the main-sequence B stars: the stars have a single iron abundance, but there is a star-to-star variation of oxygen abundance. Oxygen-rich and oxygen-poor stars are roughly segregated on the sky.