High frequency gravitational radiation and ringing down of an isolated gravitating system

A qualitative description is given of the gravitational field of an isolated gravitating system emitting high frequency gravitational radiation which is ended by a burst of radiation accompanied by matter travelling with the speed of light, which in turn is followed by an exponential ringing down to the field of a spherical black hole. The process we describe could conceivably be applied to the last stages of a binary neutron star collision. In this case the high frequency phase coincides with the rapid inspiral motion of the stars. This is ended by the collision, giving rise to a burst of outgoing radiation accompanied by light-like matter such as neutrinos, and then the ringing down follows when the remnant of the collision rapidly radiates away its wave-front anisotropy, and a spherical black hole is formed.