EDP Sciences
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Volume 482, Number 2, May I 2008
Page(s) L5 - L8
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20079342
Published online 11 March 2008

A&A 482, L5-L8 (2008)
DOI: 10.1051/0004-6361:20079342


The exoplanet-host star $\iota$ Horologii: an evaporated member of the primordial Hyades cluster

S. Vauclair1, M. Laymand1, F. Bouchy2, G. Vauclair1, A. Hui Bon Hoa1, S. Charpinet1, and M. Bazot3

1  Laboratoire d'Astrophysique de Toulouse-Tarbes, CNRS, Université de Toulouse, 14 Av. Ed. Belin, 31400 Toulouse, France
    e-mail: svcr@ast.obs-mip.fr
2  Institut d'Astrophysique de Paris, 75014 Paris, France
3  Centro de Astrophysica da Universidade do Porto, Porto, Portugal

(Received 30 December 2007 / Accepted 4 March 2008)

Aims. We show that the exoplanet-host star iota Horologii, alias HD 17051, 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 $\iota$ 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.

Key words: stars: oscillations -- stars: planetary systems -- stars: abundances -- Galaxy: open cluster and associations: individual: Hyades

© ESO 2008

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