DETAILED ABUNDANCES OF THE SOLAR TWINS 16 CYGNI A AND B: CONSTRAINING PLANET FORMATION MODELS

Abstract

Results of a detailed abundance analysis of the solar twins 16 Cyg A and 16\nCyg B based on high-resolution, high signal-to-noise ratio echelle spectroscopy\nare presented. 16 Cyg B is known to host a giant planet while no planets have\nyet been detected around 16 Cyg A. Stellar parameters are derived directly from\nour high-quality spectra, and the stars are found to be physically similar,\nwith Delta_T_eff = +43 K, Delta_logg = -0.02 dex, and Delta_xi = +0.10 km/s (in\nthe sense of A - B), consistent with previous findings. Abundances of 15\nelements are derived and are found to be indistinguishable between the two\nstars. The abundances of each element differ by <= 0.026 dex, and the mean\ndifference is +0.003 +/- 0.015 (sigma) dex. Aside from Li, which has been\npreviously shown to be depleted by a factor of at least 4.5 in 16 Cyg B\nrelative to 16 Cyg A, the two stars appear to be chemically identical. The\nabundances of each star demonstrate a positive correlation with the\ncondensation temperature of the elements (T_c); the slopes of the trends are\nalso indistinguishable. In accordance with recent suggestions, the positive\nslopes of the [m/H]-T_c relations may imply that terrestrial planets have not\nformed around either 16 Cyg A or 16 Cyg B. The physical characteristics of the\n16 Cyg system are discussed in terms of planet formation models, and plausible\nmechanisms that can account for the lack of detected planets around 16 Cyg A,\nthe disparate Li abundances of 16 Cyg A and B, and the eccentricity of the\nplanet 16 Cyg B b are suggested.\n