It is one of only two pulsars known to be in orbit around a star many times the mass of our Sun. The orbit of the pulsar about its companion is very elliptical and every 3.5 years, at closest approach, the pulsar passes through the Be star's disk. The pulsar remains behind the disk and obscured from the Earth for about 30 days before it reemerges. This last occurred in May 1997 and was observed extensively by an international team of scientists coordinated by Simon Johnston. At about the same time unpulsed radio emission suddenly appears.
All pulsars produce a wind of highly energetic electrons.
The same process is thought to produce the unpulsed radio emission observed from some other pulsars. However, Lewis and his collaborators have shown that although the unpulsed radio emission from PSR B1259-63 is synchrotron radiation, it cannot be produced by particles from the pulsar wind. They argue that the emission comes from electrons from the Be star disk which are accelerated at a shock wave produced as the pulsar crashes through the disk. The characteristic twin peaked structure of the unpulsed radio brightness variation arises as the pulsar plows through the disk just before its closest approach to the Be star producing the first peak, disappears behind the disk for a short time, and then plows back through the disk on the other side of the star. Also indicated is the pulsar wind interacting with the disk, and the pulsar orbit, the dashed part of which is behind the plane of the sky.