A model for the superhumps in cataclysmic variables

Two cataclysmic variables, VW Hyi and WZ Sge, have now been seen to display a photometric period, Psub(r), during outburst (or superoutburst for VW Hyi) which is greater than the photometric period seen during quiescence by a few per cent. It is proposed that the orbits of these stars are slightly eccentric (e approximately 10-4) and that Psub(r) is the period on which the mass-transfer rate is modulated, due to periodic variation of the stellar separation. Thus Psub(r) is related to the orbital period P and the apsidal precession period U by Psub(r)-P = P2/U. (author)