Gravitational signals due to tidal interactions between white dwarfs and black holes

In this paper, we compute the gravitational signal emitted when a white dwarf moves around a black hole on a closed or open orbit using the affine-model approach. We compare the orbital and the tidal contributions to the signal, assuming that the star moves in a safe region where, although very close to the black hole, the strength of the tidal interaction is insufficient to provoke the stellar disruption. We show that for all considered orbits the tidal signal presents sharp peaks corresponding to the excitation of the non-radial oscillation modes of the star, the amplitude of which depends on how deep the star penetrates the black hole tidal radius and on the type of orbit. Further structure is added to the emitted signal by the coupling between the orbital and the tidal motions.