An Origin for Pulsar Kicks in Supernova Hydrodynamics

It is now believed that pulsars comprise the fastest population of stars in the galaxy. With inferred mean, root-mean-square, and maximum 3-D pulsar speeds of $\sim$300-500 km/s, $\sim$500 km/s, and $\sim$2000 km/s, respectively, the question of the origin of such singular proper motions becomes acute. What mechanism can account for speeds that range from zero to twice the galactic escape velocity? We speculate that a major vector component of a neutron star’s proper motion comes from the hydrodynamic recoil of the nascent neutron star during the supernova explosion in which it is born. Recently, theorists have shown that asymmetries and instabilities are a natural aspect of supernova dynamics. In this paper, we highlight two phenomena: 1) the Brownian-like'' stochastic motion of the core in response to the convective boiling’’ of the mantle of the protoneutron star during the post-bounce, pre-explosion accretion phase, and 2) the asymmetrical bounce and explosion of an aspherically collapsing Chandrasekhar core.In principle,either phenomenon can leave the young neutron star with a speed of hundreds of kilometers per second.