  It is shown that if an asymptotically flat spacetime is asymptotically
stationary, in the sense that $\Lie_{\xi} g_{ab}$ vanishes at the rate $\sim
t^{-3}$ for asymptotically timelike vector field $\xi^a$, and the
energy-momentum tensor vanishes at the rate $\sim t^{-4}$, then the spacetime
is an asymptotically Schwarzschild spacetime. This gives a new aspect of the
uniqueness theorem of a black hole.
