  Sakurai's object is a born again AGB star of the very late thermal pulse
flavor. In this contribution I will discuss new models of stellar evolution and
nucleosynthesis models of this phase. Two most intriguing properties of
Sakurai's objects have so far not been understood theoretically: the peculiar
chemical appearance, in particular the high lithium abundance and the short
time scale of only a few years on which the transition from the dwarf
configuration into the born again giant appearance has occurred. A new
nucleosynthesis mode of hot hydrogen-deficient He3 burning can explain the
extraordinary lithium abundance. During the thermal pulse He3 is ingested from
the envelope together with the protons into the hot He-flash convection zone.
The first network calculations show that due to the large C12 abundance protons
are rather captured by carbon than destroy newly formed Be7 and ultimately Li7.
Moreover, the short evolution time scale has been reproduced by making the
assumption that the convective efficiency for element mixing is smaller by two
to three orders of magnitude than predicted by the mixing-length theory. As a
result the main energy generation from fast convective proton capture will
occur at a larger mass coordinate, closer to the surface and the expansion to
the giant state is accelerated to a few years in agreement with Sakurai's
behavior. This result may represent an independent empirical constraint on the
poorly known efficiency of element mixing in convective zones of the stellar
interior.
