Detecting circumbinary exoplanets and hierarchical stellar triples with
  the LISA gravitational radiation mission
  We investigate the possibility of detecting planetary or stellar companions
orbiting white dwarf binaries using the LISA gravitational radiation detector.
Specifically, we consider the acceleration of the barycenter of the white dwarf
binary due to the orbiting third body as well as the effect of changes in the
tidal field across the binary due to the perturber's eccentric orbit. We find
that the movement of the barycenter is detectable for both stellar and
planetary mass objects. If circumbinary planets occur with frequencies similar
to gas giant planets around isolated main sequence stars, then we expect to
find of order 10 such planets in four years of LISA observations. For a longer,
ten-year mission the accessible parameter space for planetary mass, orbital
period, and binary orbital period grows and LISA's associated yield increases
to ~100 expected detections.
