A method to estimate stellar ages from kinematical data
  We present a method to build a probability density function (pdf) for the age
of a star based on its peculiar velocities $U$, $V$ and $W$ and its orbital
eccentricity. The sample used in this work comes from the Geneva-Copenhagen
Survey (GCS) which contains both the spatial velocities, orbital eccentricities
and isochronal ages for about $14\,000$ stars. Using the GCS stars, we fitted
the parameters that describe the relations between the distributions of
kinematical properties and age. This parametrization allows us to obtain an age
probability from the kinematical data. From this age pdf, we estimate an
individual average age for the star using the most likely age and the expected
age. We have obtained the stellar age pdf for the age of $9\,102$ stars from
the GCS and have shown that the distribution of individual ages derived from
our method is in good agreement with the distribution of isochronal ages. We
also observe a decline in the mean metallicity with our ages for stars younger
than 7 Gyr, similar to the one observed for isochronal ages. This method can be
useful for the estimation of rough stellar ages for those stars that fall in
areas of the HR diagram where isochrones are tightly crowded. As an example of
this method, we estimate the age of Trappist-1, which is a M8V star, obtaining
the age of $t(UVW) = 12.50(+0.29-6.23)$ Gyr.
