OXYGEN AND NITROGEN ABUNDANCES IN HYADES F-TYPE DWARFS

The abundances of oxygen and nitrogen were investigated for eleven Hya des F type main-sequence stars, based on the line-profile of O I (+Fe I) 8446 and the equivalent-widths of NI 8629/8683, in order to examine whether any conspicuous abundance deficiency exists for O and N at T- off similar to 6700 K similar to that observed for Li, since its possi bility was suggested by the diffusion interpretation of this ''Li-chas m''. It turned out, however, that the abundances appear to be nearly i ndependent of T-eff (and upsilon(c) sin i) for both O and N, without s howing any apparent dip larger than similar to 0.2 dex (for O) or simi lar to 0.3 dex (for N), being consistent with the results of Garcia-Lo pez et al.'s (1993, AAA 58.114.068) study for oxygen. This may indicat e that the diffusion process alone is probably not responsible for the origin of the Li-gap. Regarding the averaged O and N abundances in th ese Hyades F stars, a moderate N-excess by similar to 0.3 dex relative to the Sun was suggested (though not definite), with oxygen being nea rly normal.