By using the high-dispersion spectra of 14 bright planet-harboring stars
(along with 4 reference stars) observed with the new coude echelle spectrograph
at Okayama Astrophysical Observatory, we investigated the abundances of
volatile elements (C, N, O, S, Zn; low condensation temperature Tc) in order to
examine whether these show any significant difference compared to the
abundances of other refractory elements (Si, Ti, V, Fe, Co, Ni; high Tc) which
are known to be generally overabundant in those stars with planets, since a
Tc-dependence is expected if the cause of such a metal-richness is due to the
accretion of solid planetesimals onto the host star. We found, however, that
all elements we studied behave themselves quite similarly to Fe (i.e.,
[X/Fe]~0) even for the case of volatile elements, which may suggest that the
enhanced metallicity in those planet-bearing stars is not so much an acquired
character (by accretion of rocky material) as rather primordial.Comment: 22 pages, 8 figures, to appear in PAS
