  We present detailed modelling of the exoplanet-host star Mu Arae, using a new
method for the asteroseismic analysis, and taking into account the new value
recently derived for the Hipparcos parallax. The aim is to obtain precise
parameters for this star and its internal structure, including constraints on
the core overshooting. We computed new stellar models in a wider range than
Bazot et al. (2005), with various chemical compositions ([Fe/H] and Y), with or
without overshooting at the edge of the core. We computed their adiabatic
oscillation frequencies and compared them to the seismic observations. For each
set of chemical parameters, we kept the model which represented the best fit to
the echelle diagram. Then, by comparing the effective temperatures, gravities
and luminosities of these models with the spectroscopic error boxes, we were
able to derive precise parameters for this star. First we find that all the
models which correctly fit the echelle diagram have the same mass and radius,
with an uncertainty of the order of one percent. Second, the final comparison
with spectroscopic observations leads to the conclusion that besides its high
metallicity, Mu Arae has a high helium abundance of the order of Y=0.3. Knowing
this allows finding precise values for all the other parameters, mass, radius
and age.
