Simply put, either by chance or a suicidal type-III Civilization, 2 neutron stars, or a neutron star an a large-ish main sequence star are thrown at eachother and fall STRAIGHT into eachother. What happens? Does the ~1.4 C Newtonian impact speed result in them getting blown up and releasing their mass-energy into the universe? making a black hole? something else? For the sake of consistency, let us assume that each neutron star is 2 Solar masses with a radius of 6 km, this also happens to be hovering on the edge of becoming a black hole. (pciked values arbitrarily, got 99.5C as escape velocity.) By the way, preliminary calculations of the mass-energy of each seem to indicate a yield of 6.4E47 Joules, if that is what would happen.