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Centro de Astrofísica da Universidade do Porto

Accurate abundance patterns of solar twins and analogs
Does the anomalous solar chemical composition come from planet formation?

I. Ramírez, J. Meléndez, M. Asplund

Abstract
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 ≃ 60 000), high signalto-noise ratio (S/N ≃ 200) spectra. The estimated errors in the elemental abundances relative to solar are as small as ≃0.025 dex. 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 (TC). In the sample of 22 stars with parameters closest to solar, we find that, on average, low TC elements are depleted with respect to high TC elements in the solar twins relative to the Sun by about 0.08 dex (≃20%). An increasing trend is observed for the abundances as a function of TC for 900 < TC < 1800K, while abundances of lower TC 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.

Keywords
stars: abundances - Sun: abundances - planetary systems

Notes
Figure 1 and Tables 1–4 are only available in electronic form at http://www.aanda.org

Astronomy and Astrophysics
Volume 508, Page L17
December 2009

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