  Warm jupiters are an unexpected population of extrasolar planets that are too
near to their host to have formed in situ, but distant enough to retain a
significant eccentricity in the face of tidal damping. These planets are
curiously absent around stars larger than two solar radii. We hypothesize that
the warm jupiters are migrating due to Kozai-Lidov oscillations, which leads to
transient episodes of high eccentricity and a consequent tidal decay.
  As their host evolves, such planets would be rapidly dragged in or engulfed
at minimum periapse, leading to a rapid depletion of the population with
increasing stellar radius, as is observed. Using numerical simulations, we
determine the relationship between periapse distance and orbital migration rate
for planets 0.1 to 10 Jupiter masses and with orbital periods between 10 and
100 days. We find that Kozai-Lidov oscillations effectively result in planetary
removal early in the evolution of the host star, possibly accounting for the
observed deficit. While the observed eccentricity distribution is inconsistent
with the simulated distribution for an oscillating and migrating warm jupiter
population, observational biases may explain the discrepancy.
