Satellites in discs: regulating the accretion luminosity

We demonstrate, using a simple analytic model, that the presence of a massive satellite can globally modify the structure and emission properties of an accretion disc to which it is tidally coupled. We show, using two levels of numerical approximation, that the analytic model gives reasonable results. The results are applicable to two astrophysical situations. For an active galactic nucleus, we consider the case of a ~ 103 M⊙ compact companion to the central black hole, and show that it could modulate the emitted spectrum on a time-scale of ~ 105 yr. In the case of a T Tauri accretion disc, a satellite such as a subdwarf or giant planet could modify the disc spectral energy distribution over a substantial fraction of the T Tauri star lifetime.