Separated at Birth: The Origin of the Pulsars B2020+28 and B2021+51 in the Cygnus Superbubble

Abstract

High-precision astrometric data have enabled us to determine the trajectories through the Galactic potential for a growing number of pulsars. This has resulted in the discovery of a pulsar pair (B2020+28 and B2021+51) that has a common origin in the Cygnus superbubble or in one of its related OB associations at an epoch that is comparable to the spin-down ages of the pulsars. Analysis of the Galactic orbits indicates that the progenitors of the pulsars had similar masses and were in a binary system that was disrupted after the second supernova explosion. The implied pulsar birth velocities are consistent with the high velocities of neutron stars in general. The initial spin period of the pulsar that was formed in the second supernova explosion was ~200 ms. A further increase in astrometric accuracy will allow us to more tightly constrain the birth velocities and the kick velocities that were imparted by the two supernova explosions. Two additional pulsars in the sample of 24 with parallax measurements may also have originated in the Cygnus superbubble.