Coplanar Circumbinary Planets Can Be Unstable to Large Tilt Oscillations in the Presence of an Inner Polar Planet

Childs, Anna C.; Martin, Rebecca G.; Lepp, S.; Lubow, Stephen H.; Geller, Aaron M.

doi:10.3847/2041-8213/acbcc9

Cited by 3 publications

(2 citation statements)

References 51 publications

(58 reference statements)

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“…In the limit of a small-mass companion, the nodal precession of the outer body driven by the inner body is et al 1997;Childs et al 2023), where k 2 is the gravitational constant.…”

Section: Analytic Resultsmentioning

confidence: 99%

“…GR always causes the inner binary to precess in a prograde direction, while the direction of the precession induced by companion depends upon its inclination. At inclinations near to 90°the precession caused by the companion is retrograde (e.g., Zhang & Fabrycky 2019;Childs et al 2023), whereas close to i = 0 and i = 180°it is prograde. The stationary inclination increases rapidly for companions with a mass of about 1 M e and a separation of about 10 a b because as the companion approaches i = 180°, the precession of the binary speeds up.…”

Section: Dynamics Of the Three-body Systemsmentioning

confidence: 99%

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Black Hole Mergers Driven by a Captured Low-mass Companion

Lepp,

Martin,

Zhang

2023

ApJL

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Increased eccentricity of a black hole binary leads to reduced merger times. With n-body simulations and analytic approximations including the effects of general relativity (GR), we show that even a low-mass companion orbiting a black hole binary can cause significant eccentricity oscillations of the binary as a result of the Kozai–Lidov mechanism. A companion with a mass as low as about 1% of the binary mass can drive the binary eccentricity up to ≳0.8, while a mass of a few percent can drive eccentricities greater than 0.98. For low-mass companions, this mechanism requires the companion to be on an orbit that is closer to retrograde than to prograde to the binary orbit, and this may occur through capture of the third body. The effects of GR limit the radial range for the companion for which this mechanism works for the closest binaries. The merger timescale may be reduced by several orders of magnitude for a captured companion mass of only a few percent of the binary mass.

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“…In the limit of a small-mass companion, the nodal precession of the outer body driven by the inner body is et al 1997;Childs et al 2023), where k 2 is the gravitational constant.…”

Section: Analytic Resultsmentioning

confidence: 99%

Section: Dynamics Of the Three-body Systemsmentioning

confidence: 99%

Black Hole Mergers Driven by a Captured Low-mass Companion

Lepp,

Martin,

Zhang

2023

ApJL

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Inclination instability of circumbinary planets

Lubow,

Childs,

Martin

2024

Monthly Notices of the Royal Astronomical Society

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We analyze a tilt instability of the orbit of an outer planet in a two planet circumbinary system that we recently reported. The binary is on an eccentric orbit and the inner circumbinary planet is on a circular polar orbit that causes the the binary to undergo apsidal precession. The outer circumbinary planet is initially on a circular or eccentric orbit that is coplanar with respect to the binary. We apply a Hamiltonian in quadrupole order of the binary potential to show that the tilt instability is the result of a secular resonance in which the apsidal precession rate of the binary matches the nodal precession rate of the outer planet. Resonance is possible because the polar inner planet causes the apsidal precession of the binary to be retrograde. The outer planet periodically undergoes large tilt oscillations for which we analytically determine the initial evolution and maximum inclination. Following a typically relatively short adjustment phase, the tilt grows exponentially in time at a characteristic rate that is of order the absolute value of the binary apsidal precession rate. The analytic results agree well with numerical simulations. This instability is analogous to the Kozai-Lidov instability, but applied to a circumbinary object. The instability fails to operate if the binary mass ratio is too extreme. The instability occurs even if the outer planet is instead an object of stellar mass and involves tilt oscillations of the inner binary.

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Mergers of black hole binaries driven by misaligned circumbinary discs

Martin,

Lepp,

Zhang

et al. 2023

Monthly Notices of the Royal Astronomical Society: Letters

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With hydrodynamical simulations we examine the evolution of a highly misaligned circumbinary disc around a black hole binary including the effects of general relativity. We show that a disc mass of just a few percent of the binary mass can significantly increase the binary eccentricity through von-Zeipel–Kozai–Lidov (ZKL) like oscillations provided that the disc lifetime is longer than the ZKL oscillation timescale. The disc begins as a relatively narrow ring of material far from the binary and spreads radially. When the binary becomes highly eccentric, disc breaking forms an inner disc ring that quickly aligns to polar. The polar ring drives fast retrograde apsidal precession of the binary that weakens the ZKL effect. This allows the binary eccentricity to remain at a high level and may significantly shorten the black hole merger time. The mechanism requires the initial disc inclination relative to the binary to be closer to retrograde than to prograde.

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Coplanar Circumbinary Planets Can Be Unstable to Large Tilt Oscillations in the Presence of an Inner Polar Planet

Cited by 3 publications

References 51 publications

Black Hole Mergers Driven by a Captured Low-mass Companion

Black Hole Mergers Driven by a Captured Low-mass Companion

Inclination instability of circumbinary planets

Mergers of black hole binaries driven by misaligned circumbinary discs

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