Issue |
A&A
Volume 443, Number 2, November IV 2005
|
|
---|---|---|
Page(s) | 609 - 626 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20053452 | |
Published online | 04 November 2005 |
On the ages of exoplanet host stars
Observatorio Astronómico de Córdoba, Laprida 854, 5000 Córdoba, Argentina e-mail: [saffe;mercedes;carolina]@oac.uncor.edu
Received:
17
May
2005
Accepted:
2
August
2005
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, . 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
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.
Key words: stars: chromospheres / stars: fundamental parameters / stars: kinematics / stars: planetary systems / techniques: spectroscopic
© ESO, 2005
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