http://arxiv.org/abs/1409.6717
The secular evolution of hierarchical triple systems plays an important role in many astrophysical contexts, from irregular satellites of giant planets to high-eccentricity migration of hot Jupiters and the formation of compact stellar binaries. When the mutual inclination angle between the inner and outer orbits is sufficiently high, the inner pair can experience large-amplitude Lidov-Kozai (LK) oscillations in eccentricity and inclination. 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 pericenter precession due to various short-range effects, such as General Relativity and tidal and rotational distortions, can limit the growth of eccentricity and even suppress standard (quadrupolar) LK oscillations. In this paper, we systematically study how these short-range forces affect the extreme orbital behaviour found in octupole LK cycles. In general, the influence of the octupole potential is confined to a range of initial mutual inclinations Itot (the inclination angle between the inner and outer orbits) centered around 90 deg (in the test-mass approximation, when the inner binary mass ratio is << 1), with this 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. 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 Itot around 90 deg within which flips are possible as the intensity of these forces increases.
B. Liu, D. Munoz and D. Lai
Thu, 25 Sep 14
1/58
Comments: 20 pages,15 figures, submitted to MNRAS
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