Long-term variability of x-ray binaries: the aftermath of supernovae

Arguments are given to show that the forced precession of the rotation axis of the optical star in an x-ray binary as well as the accompanying long-period optical and x-ray variability may be properties common to all x-ray binaries, having resulted from an asymmetric supernova outburst. Even a slightly anisotropic explosion in a binary system could turn the orbit plane relative to the optical-star rotation axis, whose forced precession would regularly alter the orientation of the occulting gas streams and the accretion disk structure around the relativistic object, thereby inducing long-term x-ray and optical variability of the system