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The exoplanet-host star ι Horologii: an evaporated member of the primordial Hyades cluster

S. Vauclair, M. Laymand, F. Bouchy, G. Vauclair, A. Hui-Bon-Hoa, S. Charpinet, M. Bazot


Aims. We show that the exoplanet-host star iota Horologii, alias HD17051, which belongs to the so-called Hyades stream, was formed within the primordial Hyades stellar cluster and has evaporated towards its present location, 40 pc away.
Methods. This result has been obtained unambiguously by studying the acoustic oscillations of this star, using the HARPS spectrometer in La Silla Observatory (ESO, Chili).
Results. Besides the fact that ι Hor belongs to the Hyades stream, we give evidence that it has the same metallicity, helium abundance, and age as the other stars of the Hyades cluster. They were formed together, at the same time, in the same primordial cloud.
Conclusions. This result has strong implications for theories of stellar formation. It also indicates that the observed overmetallicity of this exoplanet-host star, about twice that of the Sun, is original and not caused by planet accretion during the formation of the planetary system.

Astronomy and Astrophysics
Volume 482, Page L5
2008 April

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Instituto de Astrofísica e Ciências do Espaço Universidade do Porto Faculdade de Ciências da Universidade de Lisboa Fundação para a Ciência e a Tecnologia
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