Orbital dynamics of a binary system composed of a massive star and a black hole companion

In this work, we consider a binary system composed of a massive star and a black hole companion. By monitoring the mass transfer from the star to the black hole, we perform a thorough and systematic orbit classification for determining the final states of a test particle moving inside the gravitational field of the binary system. For this purpose, we deploy the theory of the time-independent restricted three-body problem for modeling the motion of the test particle. Our analysis strongly suggests that escaping, collisional and bounded motion dominate in different phases of the mass transport, while the overall orbital dynamics of the test particle become very intricate for larger differences between the masses of the two primaries. Moreover, the bounded motion is further classified into regular, sticky, and chaotic by using the SALI chaos indicator. © 2024 Elsevier B.V.