Modulation of the Neutron Star Boundary Layer Luminosity by Disk Oscillations

Paczyński (1987) pointed out that any modulation of the rate at which mass is accreted by a neutron star from the innermost part of a relativistic accretion disk will lead to a modulation of the luminosity of the boundary layer. Following this reasoning, we demonstrate that variability of the boundary layer X-ray flux must necessarily show frequencies of certain global accretion disk oscillations. This theoretical paradigm - clock in the disk, modulation at the boundary layer - resolves one puzzling paradox in the neutron star quasi periodic oscillation (QPO) data.