The refining process forms the remnant into a spherical shape and usually generates a loud burst of gravitational waves which then fade off. Supernovas aren't really understood too well. Again, some parts are higher in the gravitational field than others, and gravitational radiation is shed as the combined lump of neutron star becomes more and more spherical. If we're really lucky, the coalesced form will be too big and form a black hole . B inaries of two black holes would do much the same, except they're a lot more interesting and radiate a lot more gravitational waves.
Neutron stars are typically a few kilometers in diameter.
Black holes are smaller than neutron stars by far and can get much closer, spinning much faster, before they being to coalesce. The closer they get and the faster they spin around each other generates a stronger wave. T he difference between a neutron star binary and a black hole binary is in the coalescence stage. Instead of mushing lots of matter together like the neutron stars, the black holes merge their even horizons just like two soap bubbles joining. I'm not to clear on what the singularities do, but that's nothing new.