Tidal Excitation of Spiral Waves in Accretion Discs

Abstract

We present nonlinear calculations of the tidal interaction of an accretion disc in close binary systems with mass ratio one tenth. We consider characteristic Mach numbers for the Keplerian flow between 10 and 50. In agreement with earlier work it is found that hot, extended discs with Mach numbers M ≤ 10 are subject to strong tidal coupling with the companion star whereby the disc loses a sufficient amount of angular momentum through shock dissipation to enable disc matter to accrete onto the central star. However, for cool discs with Mach numbers M ≥ 25 thought typical for discs in e.g. Cataclysmic Variables, the wavelength of the tidal response is much shorter than the lengthscale of the tidal force so that the tidal interaction becomes inefficient and although adequate to truncate the disc, it produces little wave driven accretion onto the central star