The white dwarf population of NGC 6397
  NGC 6397 is one of the most interesting, well observed and theoretically
studied globular clusters. The existing wealth of observations allows us to
study the reliability of the theoretical white dwarf cooling sequences of low
metallicity progenitors,to determine its age and the percentage of unresolved
binaries, and to assess other important characteristics of the cluster, like
the slope of the initial mass function, or the fraction of white dwarfs with
hydrogen deficient atmospheres. We present a population synthesis study of the
white dwarf population of NGC 6397. In particular, we study the shape of the
color-magnitude diagram, and the corresponding magnitude and color
distributions. We do this using an up-to-date Monte Carlo code that
incorporates the most recent and reliable cooling sequences and an accurate
modeling of the observational biases. We find a good agreement between our
theoretical models and the observed data. In particular, we find that this
agreement is best for those cooling sequences that take into account residual
hydrogen burning. This result has important consequences for the evolution of
progenitor stars during the thermally-pulsing asymptotic giant branch phase,
since it implies that appreciable third dredge-up in low-mass, low-metallicity
progenitors is not expected to occur. Using a standard burst duration of 1.0
Gyr, we obtain that the age of the cluster is 12.8+0.50-0.75 Gyr. Larger ages
are also compatible with the observed data, but then realistic longer durations
of the initial burst of star formation are needed to fit the luminosity
function. We conclude that a correct modeling of the white dwarf opulation of
globular clusters, used in combination with the number counts of main sequence
stars provides an unique tool to model the properties of globular clusters.
