THE PROPAGATION OF ACOUSTIC-WAVES AND QUASI-PERIODIC OSCILLATIONS IN ACCRETION DISC BOUNDARY-LAYERS

We provide one-dimensional time-dependent calculations of optically th ick and geometrically thin accretion disc boundary layers in cataclysm ic variables (CVs), by using the Chebyshev spectral method. Our numeri cal calculations show that the properties of quasi-periodic oscillatio ns (QPOs) are characteristic of acoustic waves propagating in the inne r region of accretion discs for low values of alpha. Moreover, the obs ervations provide significant evidence in support of the acoustic natu re of the QPOs. The relative amplitudes of the QPOs (as observed in th e optical and the X-ray), the autocorrelation function of their light curve, and the relation between the QPO periods and their decay times are all characteristic of acoustic waves.