On the ages of exoplanet host stars

SAFFE, C., GOMEZ, M., CHAVERO, C.

EDP SCIENCES S A

Lugar: Paris; Año: 2005 p. 609 - 609

e 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, R´_HK. 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