Invited Presentation

Suppression of extreme orbital evolution in triple systems with short range forces

Author(s): Bin Liu (Shanghai Astronomical Observatory)

Presenter: Bin Liu (Shanghai Astronomical Observatory)

The Lidov-Kozai mechanism plays an important role in the secular evolution of hierarchical triple systems. Recent work has shown that when the octupole terms are included in the interaction potential, the inner binary can undergo extreme eccentricity excitation as well as inclination flips with respect to the outer orbit. It has also been recognized that pericentre precession due to various short-range effects, such as General Relativity, tidal and rotational distortions, can limit the growth of eccentricity and even suppress standard (quadrupole) Lidov-Kozai oscillations. Here, we systematically study how these short-range forces affect the extreme orbital behavior found in octupole Lidov-Kozai cycles. In general, the influence of the octupole potential is confined to a range of initial mutual inclinations (the inclination angle between the inner and outer orbits) centered around 90 degrees (in the test-mass approximation, when the inner binary mass ratio is << 1), with the range expanding with increasing octupole strength. We find that, while the short-range forces do not change (the width and location of) this “window of influence”, they impose a strict upper limit on the maximum achievable eccentricity (within this window). This limiting eccentricity can be calculated analytically, and its value holds even for very strong octupole potential and for the general case of three comparable masses. Short-range forces also affect orbital flips, progressively reducing the range of the mutual inclinations around 90 degrees within which flips are possible as the intensity of these forces is increased.