New Post-AGB star models as tools to understand AGB evolution and
  nucleosynthesis
  We study a sample of post-AGB stars in the Galaxy, with known surface
chemical composition and s-process enrichment. The recent determination of the
luminosities of these sources, based on Gaia parallaxes, allows for the fist
time a deep investigation of Galactic post-AGB stars, with the possibility of
characterising the individual objects in terms of mass, chemical composition
and age of the progenitors. To this aim we used available evolutionary
sequences of AGB stars, extended to the post-AGB phase, complemented by new
models, specifically calculated for the present study. The combined knowledge
of the surface carbon and of the luminosity proves the most valuable indicator
of the previous history of the star, particularly for what regards the
efficiency of the various mechanisms able to alter the surface chemical
composition and the growth of the core mass. This kind of analysis allows
dissecting different classes of stars, such as low-mass objects, that evolved
as M-type stars for the whole AGB lifetime, carbon stars, massive AGB stars
that experienced hot bottom burning. The potentialities of this approach to
shed new light on still debated issues related to the AGB evolution are also
commented.
