The C and N abundances in disk stars

Abundance analysis of carbon and nitrogen has been performed for a sample of 90 F and G type mainsequence disk stars with a metallicity range of -1.0 < [Fe/H] < +0.2 using the Cl and N I lines. We confirm a moderate carbon excess in the most metal-poor disk dwarfs found in previous investigations. Our results suggest that carbon is enriched by superwinds of metal-rich massive stars at the beginning of the disk evolution, while a significant amount of carbon is contributed by low-mass stars in the late stage. The observed behavior of [N/Fe] is about solar in the disk stars, irrespective of the metallicity. This result suggests that nitrogen is produced mostly by intermediate-mass stars.