  We point out that a soliton such as an oscillon or boson star inevitably
decays into gravitons through gravitational interactions. These decay processes
exist even if there are no apparent self-interactions of the constituent field,
scalar or vector, since they are induced by gravitational interactions. Hence,
our results provide a strict upper limit on the lifetime of oscillons and boson
stars including the dilute axion star. We also calculate the spectrum of the
graviton background from decay of solitons.
