Influence of the Lense–Thirring effect on stellar orbits around a spinning supermassive black hole

Abstract

Rotating super-massive black holes drive Lense-Thirring effects, which induce orbit nodal and eccentricity vector precession in their vicinity. Typically, these relativistic effects are quite small, but for the case of close-in orbits that are additionally perturbed by an outer intermediate mass companion (IMC), we show that the Lense-Thirring effects can lead to markedly different dynamical behaviour. Using REBOUND N-body simulations, we show that resonances occur considering both the Lense-Thirring effect and secular perturbations from the IMC, and it can excite the inclination of the orbits, an order of magnitude higher than that achieved solely due to secular three-body effects. We also examine the sensitivity of the inclination growth on the profile of the IMC and find that the excitation is highest for a companion to SMBH mass ratio of 1:1000 and for companions that orbit the SMBH on closer-in orbits. In addition, we investigate how varying the spin direction of the SMBH affects the inclination of the orbits. We find no excitation in the eccentricity of the orbits since the resonance is on the nodal angle, and the fast precession suppresses Kozai cycles. Finally, we note how the Lense-Thirring effect reduces the stability of the three-body system, enhancing the scattering rate between the test particles and the IMC, and thus making disruption events more likely in the system.