  A significant fraction of stars are members of gravitationally bound
hierarchies containing three or more components. Almost all low mass stars in
binaries with periods shorter three days are part of a hierarchical system. We
therefore anticipate that a large fraction of compact galactic binaries
detected by the Laser Interferometer Space Antenna (LISA) will be members of
hierarchical triple or quadruple system. The acceleration imparted by the
hierarchical companions can be detected in the gravitational wave signal for
outer periods as large as 100 years. For systems with periods that are shorter
than, or comparable to, the mission lifetime, it will be possible to measure
the period and eccentricity of the outer orbit. LISA observations of
hierarchical stellar systems will provide insight into stellar evolution,
including the role that Kozai-Lidov oscillations play in driving systems
towards merger.
