Published online by Cambridge University Press: 12 April 2016
Spectroscopic observations of two very different objects are discussed: the first, SS433, is a wery massive binary system probably containing an unseen 0 or WR star and a black hole surrounded by a luminous precessing accretion disk (from which emanate spectacular relativistic jets); the second, GK Per, is a classical old nova consisting of a slightly evolved K2 star and an unseen white dwarf companion surrounded by an accretion disk which is less luminous than the K2 star.