Secular dynamics of binaries in stellar clusters – III. Doubly averaged dynamics in the presence of general-relativistic precession

Hamilton, Chris; Rafikov, Roman R.

doi:10.1093/mnras/stab1284

Cited by 12 publications

(3 citation statements)

References 35 publications

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“…At small separations, but before the orbits are circularised, tidal forces and the spin of the stars cause precessions which may compete with the GR precession. The precession due to these other processes can be quite complicated and depends on the exact composition and structure of the two stars (Sterne 1939;Sirotkin & Kim 2009) or compact objects (Hamilton & Rafikov 2021).…”

Section: Discussionmentioning

confidence: 99%

A radial limit on polar circumbinary orbits from general relativity

Lepp,

Martin,

Childs

2022

Preprint

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A particle orbiting a misaligned eccentric orbit binary undergoes nodal precession either around the binary angular momentum vector (a circulating orbit) or around a stationary inclination (a librating orbit). In the absence of general relativity, the stationary inclination is inclined by 90 • to the binary angular momentum vector (aligned with the binary eccentricity vector) and does not depend on the particle semi-major axis. General relativity causes apsidal precession of the binary orbit. Close to the binary, the behaviour of the particle is not significantly affected, a librating particle precesses with the binary. However, we find that the stationary inclination and the minimum inclination required for libration both increase with the particle semi-major axis. There is a critical radius beyond which there are no librating orbits, only circulating orbits, and therefore there is a maximum orbital radius for a stationary polar orbiting body. The critical radius is within planet forming regions around binaries with semi-major axis 1 au. This has implications for the search for misaligned circumbinary planets and the radial extent of polar circumbinary disks.

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Section: Discussionmentioning

confidence: 99%

A radial limit on polar circumbinary orbits from general relativity

Lepp,

Martin,

Childs

2022

Preprint

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“…In either scenario, the key idea is that secular tidal forcing can increase a binary's eccentricity dramatically. Provided this forcing is strong enough to overcome 1pN general relativistic (GR) apsidal precession, which acts to decrease the maximum eccentricity (Wen 2003;Hamilton & Rafikov 2021), the binary can thereby achieve a small pericenter distance, allowing it to radiate gravitational waves (GWs) efficiently and thus rapidly merge. Similar mechanisms have been invoked to explain the origin of other exotic objects, such as Type 1a supernovae (Katz & Dong 2012), blue stragglers (Leigh et al 2018), hot Jupiters (Fabrycky & Tremaine 2007), and so on.…”

Section: Introductionmentioning

confidence: 99%

Relativistic Phase Space Diffusion of Compact Object Binaries in Stellar Clusters and Hierarchical Triples

Hamilton,

Rafikov

2024

ApJ

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The LIGO/Virgo detections of compact object mergers have posed a challenge for theories of binary evolution and coalescence. One promising avenue for producing mergers dynamically is through secular eccentricity oscillations driven by an external perturber, be it a tertiary companion (as in the Lidov–Kozai, LK, mechanism) or the tidal field of the stellar cluster in which the binary orbits. The simplest theoretical models of these oscillations use a “doubly averaged” (DA) approximation, averaging both over the binary’s internal Keplerian orbit and its “outer” barycentric orbit relative to the perturber. However, DA theories do not account for fluctuations of the perturbing torque on the outer orbital timescale, which are known to increase a binary’s eccentricity beyond the maximum DA value, potentially accelerating mergers. Here we reconsider the impact of these short-timescale fluctuations in the test-particle quadrupolar limit for binaries perturbed by arbitrary spherical cluster potentials (including LK as a special case), in particular including 1pN general relativistic (GR) apsidal precession of the internal orbit. Focusing on the behavior of the binary orbital elements around peak eccentricity, we discover a new effect, relativistic phase space diffusion (RPSD), in which a binary can jump to a completely new dynamical trajectory on an outer orbital timescale, violating the approximate conservation of DA integrals of motion. RPSD arises from an interplay between secular behavior at extremely high eccentricity, short-timescale fluctuations, and rapid GR precession, and can change the subsequent secular evolution dramatically. This effect occurs even in hierarchical triples, but has not been uncovered until now.

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“…The primary caveat to both the LK-driven and cluster tide-driven merger mechanisms is that 1pN general relativistic (GR) apsidal precession acts to quench the oscillations and hence delay mergers. In Hamilton & Rafikov (2021)-hereafter Paper III-we provided a systematic account of how the LK-like dynamics of binaries are modified as the strength of GR precession is varied.…”

Section: Introductionmentioning

confidence: 99%

Anatomy of a Slow Merger: Dissecting Secularly Driven Inspirals of LIGO/Virgo Gravitational Wave Sources

Hamilton

Rafikov

2022

ApJ

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The dozens of compact object mergers detected by LIGO/Virgo raise a key theoretical question: how do initially wide binaries shrink sufficiently quickly that they are able to merge via gravitational wave (GW) radiation within a Hubble time? One promising class of answers involves secular driving of binary eccentricity by some external tidal perturbation. This perturbation can arise due to the presence of a tertiary point mass, in which case the system exhibits Lidov-Kozai (LK) dynamics, or it can stem from the tidal field of the stellar cluster in which the binary orbits. While these secular tide-driven mechanisms have been studied exhaustively in the case of no GW emission, when GWs are included the dynamical behavior is still incompletely understood. In this paper we consider compact object binaries driven to merger via high-eccentricity excitation by (doubly averaged, test-particle quadrupole level) cluster tides—which includes LK-driven mergers as a special case—and include the effects of both general relativistic precession and GW emission. We provide for the first time an analytical understanding of the different evolutionary stages of the binary’s semimajor axis, secular oscillation timescale, and phase-space structure all the way to merger. Our results will inform future population synthesis calculations of compact object binary mergers from hierarchical triples and stellar clusters.

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Secular dynamics of binaries in stellar clusters – III. Doubly averaged dynamics in the presence of general-relativistic precession

Cited by 12 publications

References 35 publications

A radial limit on polar circumbinary orbits from general relativity

A radial limit on polar circumbinary orbits from general relativity

Relativistic Phase Space Diffusion of Compact Object Binaries in Stellar Clusters and Hierarchical Triples

Anatomy of a Slow Merger: Dissecting Secularly Driven Inspirals of LIGO/Virgo Gravitational Wave Sources

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