Photospheric Abundances of Volatile and Refractory Elements in Planet-Harboring Stars

Abstract

Abstract By using the high-dispersion spectra of 14 bright planet-harboring stars (along with 4 reference stars) observed with the new coudé echelle spectrograph at Okayama Astrophysical Observatory, we investigated the abundances of volatile elements (C, N, O, S, Zn; low condensation temperature $T_\mathrm{c}$) 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 $T_\mathrm{c}$), which are known to be generally overabundant in those stars with planets, since a $T_\mathrm{c}$-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 which we studied behave themselves quite similarly to Fe (i.e., $[\mathrm{X} / \mathrm{Fe}] \simeq 0$), even for the case of volatile elements. This 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.