Asteroseismology of exoplanets host stars: the special case of 

Aims.This paper presents detailed analysis and modelisation of the star HD 17051 (alias ι Hor), which appears to be a specially interesting case among exoplanet host stars. Like most of these stars, ι Hor presents a metallicity excess that has been measured by various observers who give different results, ranging from [ Fe/H$] = 0.11$ to 0.26 and associated with different atmospheric parameters. Meanwhile, the luminosity of the star may be determined thanks to the Hipparcos parallax. Although it is in the southern hemisphere, this star belongs to the Hyades stream, and its external parameters show that it could even be one of the Hyades stars ejected during cluster formation. The aim of this work was to gather and analyse our present knowledge of this star and to prepare seismic tests for future observations with the HARPS spectrometer (planned for November 2006). Methods.We computed evolutionary tracks with various metallicities in the two frameworks of primordial overmetallicity and accretion. We concentrated on models inside the error boxes given by the various observers in the $\log g{-}\!\log T_{\rm eff}$ diagram. We then computed the adiabatic oscillation frequencies of these models to prepare future observations. Results.The detailed analysis of ι Hor presented in this paper has already allowed its external parameters, mass, and age to be constrained . Some values given in the literature could be rejected as inconsistent with the overall analysis. We find that a model computed with the Hyades parameters (age, metallicity) is clearly acceptable, but other ones are possible too. We are confident that observations with HARPS will allow for a clear conclusion about this star and that it will shed new light on the physics of exoplanet host stars