2002ApJ...581.1271C

If core collapse leads to the formation of a rapidly rotating, bar-unstable proto-neutron star surrounded by fallback material, then we might expect it to cool and fragment to form a double (proto-)neutron star binary in a superclose orbit. The lighter star should survive for awhile, until tidal mass loss propels it toward the minimum stable mass of a (proto-)neutron star, whereupon it explodes. Imshennik & Popov have shown that the explosion of the unstable, cold star can result in a large recoil velocity of the remaining neutron star. Here, we consider several factors that mitigate the effect and broaden the range of final recoil speeds, in particular the finite velocity and gravitational deflection of the ejecta, a range of original masses for the low-mass companion and its cooling history, rotational phase averaging of the momentum impulse from noninstantaneous mass loss, and the possibility of a common envelope phase. In spite of these mitigating factors, we argue that this mechanism can still lead to substantial neutron star recoil speeds, close to, or even above, 1000 km.s^–1.