Paper: astro-ph/0510092
Date: Tue, 4 Oct 2005 18:40:30 GMT (133kb)

Title: On the Ages of Exoplanet Host Stars

Authors: C. Saffe, M. Gomez, C. Chavero

Categories: astro-ph

Comments: 22 pages, 25 figures, A&A accepted
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We obtained spectra, covering the CaII H and K region, for 49 exoplanet host
(EH) stars, observable from the southern hemisphere. We measured the
chromospheric activity index, Rhk. We compiled previously published values of
this index for the observed objects as well as the remaining EH stars in an
effort to better smooth temporal variations and derive a more representative
value of the average chromospheric activity for each object. We used the
average index to obtain ages for the group of EH stars. In addition we applied
other methods, such as: Isochrone, lithium abundance, metallicity and
transverse velocity dispersions, to compare with the chromospheric results. The
kinematic method is a less reliable age estimator because EH stars lie red-ward
of Parenago's discontinuity in the transverse velocity dispersion vs dereddened
B-V diagram. The chromospheric and isochrone techniques give median ages of 5.2
and 7.4 Gyr, respectively, with a dispersion of 4 Gyr. The median age of F and
G EH stars derived by the isochrone technique is 1--2 Gyr older than that of
identical spectral type nearby stars not known to be associated with planets.
However, the dispersion in both cases is large, about 2--4 Gyr. We searched for
correlations between the chromospheric and isochrone ages and Lir/L* (the
excess over the stellar luminosity) and the metallicity of the EH stars. No
clear tendency is found in the first case, whereas the metallicy dispersion
seems to slightly increase with age.

\\ ( http://arXiv.org/abs/astro-ph/0510092 , 133kb)