Astronomy and Astrophysics, volume 440, 615-621 (2005/9-3)
Seismic analysis of the planet-hosting star mu Arae.
BAZOT M., VAUCLAIR S., BOUCHY F. and SANTOS N.C.
Abstract (from CDS):
Like most exoplanet host stars, HD 160691 (alias µ Ara) presents a metallicity excess in its spectrum compared to stars without detected planets. This excess may be primordial, in which case the star would be completely overmetallic, or it may be due to accretion in the early phases of planetary formation, in which case it would be overmetallic only in its outer layers. As discussed in a previous paper, seismology can help in choosing between the two scenarios. This star was observed during eight nights with the spectrograph HARPS at La Silla Observatory. Forty three p-modes were previously identified. In the present paper, we discuss the modelling of this star. We computed stellar models iterated to present the same observable parameters (luminosity, effective temperature, outer chemical composition) with differing internal structure according to the two extreme assumptions: original overmetallicity or accretion. We show that the seismic constraints lead to models in agreement with the external parameters deduced from spectroscopy and from the Hipparcos parallax (L and Teff). We show that the ``small separation'' seems to give a better fit for the accretion case than for the overmetallic case, but in spite of the very good data the uncertainties are still too large to be conclusive. We discuss the observations needed to resolve this question.