2009A&A...508L..17R

We derive the abundance of 19 elements in a sample of 64 stars with fundamental parameters very similar to solar, which minimizes the impact of systematic errors in our spectroscopic 1D-LTE differential analysis, using high-resolution (R≃60000), high signal-to-noise ratio (S/N≃200) spectra. The estimated errors in the elemental abundances relative to solar are as small as ≃0.025dex. The abundance ratios [X/Fe] as a function of [Fe/H] agree closely with previously established patterns of Galactic thin-disk chemical evolution. Interestingly, the majority of our stars show a significant correlation between [X/Fe] and condensation temperature (T_C). In the sample of 22 stars with parameters closest to solar, we find that, on average, low T_C elements are depleted with respect to high T_C elements in the solar twins relative to the Sun by about 0.08dex (≃20%). An increasing trend is observed for the abundances as a function of T_C for 900<T_C<1800K, while abundances of lower T_C elements appear to be roughly constant. We speculate that this is a signature of the planet formation that occurred around the Sun but not in the majority of solar twins. If this hypothesis is correct, stars with planetary systems like ours, although rare (frequency of ≃15%), may be identified through a very detailed inspection of the chemical compositions of their host stars.