  Field stars are frequently formed in pairs, and many of these binaries are
part of triples or even higher-order systems. Even though, the principles of
single stellar evolution and binary evolution, have been accepted for a long
time, the long-term evolution of stellar triples is poorly understood. The
presence of a third star in an orbit around a binary system can significantly
alter the evolution of those stars and the binary system. The rich dynamical
behavior in three-body systems can give rise to Lidov-Kozai cycles, in which
the eccentricity of the inner orbit and the inclination between the inner and
outer orbit vary periodically. In turn, this can lead to an enhancement of
tidal effects (tidal friction), gravitational-wave emission and stellar
interactions such as mass transfer and collisions. The lack of a
self-consistent treatment of triple evolution, including both three-body
dynamics as well as stellar evolution, hinders the systematic study and general
understanding of the long-term evolution of triple systems. In this paper, we
aim to address some of these hiatus, by discussing the dominant physical
processes of hierarchical triple evolution, and presenting heuristic recipes
for these processes. To improve our understanding on hierarchical stellar
triples, these descriptions are implemented in a public source code TrES which
combines three-body dynamics (based on the secular approach) with stellar
evolution and their mutual influences. Note that modeling through a phase of
stable mass transfer in an eccentric orbit is currently not implemented in TrES
, but can be implemented with the appropriate methodology at a later stage.
