Vol. 572
In section 8. Stellar atmospheres

The Solar Twin Planet Search. I. Fundamental parameters of the stellar sample

by I. Ramirez, J. Melendez, J. Bean, et al. A&A 572, A48


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This paper presents a detailed spectroscopic follow-up for the largest sample of solar twins (88 in all) observed at high resolution and high signal-to-noise with the MIKE optical spectrograph at Magellan. These stars are part of an ESO Large Program planet-search experiment. The authors homogeneously measure the equivalent widths of iron lines and use strict differential excitation/ionization balance analysis to determine atmospheric parameters with unprecedented internal precision: σ(Teff) = 7 K, σ(log g) = 0.019, σ([Fe/H]) = 0.006 dex, and σ(vt) = 0.016 km s−1. Reliable relative ages and very precise masses were also estimated using theoretical isochrones. The root-mean-square scatter of the differences between stars is fully compatible with the observational errors, demonstrating that systematic uncertainties in the stellar parameters are negligible. The authors also find a tight activity–age relation for their sample, which validates the internal precision of the dating method. Furthermore, the authors find that the solar cycle is perfectly consistent with boththis trend and its star-to-star scatter. The fundamental parameters derived from this work will be useful for exploring the connections between planet formation and stellar chemical composition, as well as the link to galactic chemical evolution.