Direct Measurement of Neutron Star Recoil in the Oxygen-rich Supernova Remnant Puppis A

A sequence of three Chandra X-Ray Observatory High Resolution Camera images taken over a span of five years reveals arcsecond-scale displacement of RX J0822-4300, the stellar remnant (presumably a neutron star) near the center of the Puppis A supernova remnant. We measure its proper motion to be 0.165′′ ± 0.025′′ yr-1 toward the west-southwest. At a distance of 2 kpc, this corresponds to a transverse space velocity of ~1600 km s-1. The space velocity is consistent with the explosion center inferred from proper motions of the oxygen-rich optical filaments and confirms the idea that Puppis A resulted from an asymmetric explosion accompanied by a kick that imparted roughly 3×1049 ergs of kinetic energy (some 3% of the kinetic energy for a typical supernova) to the stellar remnant. We discuss constraints on core-collapse supernova models that have been proposed to explain neutron star kick velocities.