  We study the disruption process of hierarchical 3-body systems with bodies of
comparable mass. Such systems have long survival times that vary by orders of
magnitude depending on the initial conditions. By comparing with 3-body
numerical integrations, we show that the evolution and disruption of such
systems can be statistically described as a simple random-walk process in the
outer-orbit's energy, where the energy-exchange per pericenter passage
(step-size) is calculated from the initial conditions. In our derivation of the
step-size, we use previous analytic results for parabolic encounters, and
average over the (Kozai-Lidov) oscillations in orbital parameters, which are
faster then the energy diffusion timescale. While similar random-walk models
were studied before, this work differs in two manners: (a) this is the first
time that the Kozai-Lidov averaged step-size is derived from first principles
and demonstrated to reproduce the statistical evolution of numerical ensembles
without fitting parameters, and (b) it provides a characteristic life-time,
instead of answering the binary question (stable/unstable), set by
case-specific criteria.
