The properties of 322 intermediate-mass late-G giants ( comprising 10 planet-host stars ) selected as the targets of Okayama Planet Search Program , many of which are red-clump giants , were comprehensively investigated by establishing their various stellar parameters ( atmospheric parameters including turbulent velocity fields , metallicity , luminosity , mass , age , projected rotational velocity , etc .
) , and their photospheric chemical abundances for 17 elements , in order to study their mutual dependence , connection with the existence of planets , and possible evolution-related characteristics .
The metallicity distribution of planet-host giants was found to be almost the same as that of non-planet-host giants , making marked contrast to the case of planet-host dwarfs tending to be metal-rich .
Generally , the metallicities of these comparatively young ( typical age of \sim 10 ^ { 9 } yr ) giants tend to be somewhat lower than those of dwarfs at the same age , and super-metal-rich ( [ Fe/H ] > 0.2 ) giants appear to be lacking .
Apparent correlations were found between the abundances of C , O , and Na , suggesting that the surface compositions of these elements have undergone appreciable changes due to dredge-up of H-burning products by evolution-induced deep envelope mixing which becomes more efficient for higher-mass stars .