  Elemental abundance studies of solar twin stars suggest that the solar
chemical composition contains signatures of the formation of terrestrial
planets in the solar system, namely small but significant depletions of the
refractory elements. To test this hypothesis, we study stars which, compared to
solar twins, have less massive convective envelopes (therefore increasing the
amplitude of the predicted effect) or are, arguably, more likely to host
planets (thus increasing the frequency of signature detections). We measure
relative atmospheric parameters and elemental abundances of a late-F type dwarf
sample (52 stars) and a sample of metal-rich solar analogs (59 stars). We
detect refractory-element depletions with amplitudes up to about 0.15 dex. The
distribution of depletion amplitudes for stars known to host gas giant planets
is not different from that of the rest of stars. The maximum amplitude of
depletion increases with effective temperature from 5650 K to 5950 K, while it
appears to be constant for warmer stars (up to 6300 K). The depletions observed
in solar twin stars have a maximum amplitude that is very similar to that seen
here for both of our samples. Gas giant planet formation alone cannot explain
the observed distributions of refractory-element depletions, leaving the
formation of rocky material as a more likely explanation of our observations.
More rocky material is necessary to explain the data of solar twins than
metal-rich stars, and less for warm stars. However, the sizes of the stars'
convective envelopes at the time of planet formation could be regulating these
amplitudes. Our results could be explained if disk lifetimes were shorter in
more massive stars, as independent observations indeed seem to suggest.
