  Precise abundances of 18 elements have been derived for ten stars known to
host giant planets from high signal-to-noise ratio, high-resolution echelle
spectroscopy. Internal uncertainties in the derived abundances are typically
<=0.05 dex. The stars in our sample have all been previously shown to have
abundances that correlate with the condensation temperature (T_c) of the
elements in the sense of increasing abundances with increasing T_c; these
trends have been interpreted as evidence that the stars may have accreted
H-depleted planetary material. Our newly derived abundances also correlate
positively with T_c, although slopes of linear least-square fits to the
[m/H]-T_c relations for all but two stars are smaller here than in previous
studies. When considering the refractory elements (T_c > 900 K) only, which may
be more sensitive to planet formation processes, the sample can be separated
into a group with positive slopes (four stars) and a group with flat or
negative slopes (six stars). The four stars with positive slopes have very
close-in giant planets (three at 0.05 AU) and slopes that fall above the
general Galactic chemical evolution trend. We suggest that these stars have
accreted refractory-rich planet material but not to the extent that would
increase significantly the overall stellar metallicity. The flat or negative
slopes of the remaining six stars are consistent with recent suggestions of a
planet formation signature, although we show that the trends may be the result
of Galactic chemical evolution.
