  It is shown that gravitational radiation can bind two initially unbound
bodies; no third body is needed. Such captured bodies will almost always
inspiral and merge due to further gravitational radiation on cosmologically
negligible time scales (e.g., @ 5 years for GW150914). The capture
cross-section $\sigma$ for such "capture and inspiraling" is far larger, for
initial relative speed of the two objects $v_\infty\ll c$, than that
$\sigma_{d}$ for "direct capture": $\sigma\propto\left(c /
v_\infty\right)^{18/7}$, while $\sigma_{d}\propto\left(c / v_\infty\right)^2$.
Implications of these results for black hole binary mergers, and giant black
holes at galactic centers, are discussed.
