Metallicities in Four Planet-Harbouring K-Type Giants: HD 47536, HD 59686, HD 137759, and HD 219449

Spectroscopic abundance analyses are carried out for four K-type giant stars that have recently been reported to be accompanied by giant planets, together with two reference stars of similar spectral types. The resulting metallicities, [Fe/H], for three stars (HD 59686, HD 137759, and HD 219449) coincide with the solar value, while that for HD 47536 is definitely lower than the Sun. Combining with the reported low metallicity found for the G9 III giant HD 104985 (which has a planet with an orbital period 198 days), there is no known metal-rich star with planets among giant stars. This may suggest a lower frequency of incidence of high-metallicity stars for giant stars with planets when compared with dwarf stars with planets.