Preferential Accretion and Circumbinary Disk Precession in Eccentric Binary Systems

Siwek, Magdalena Elisabeth; Weinberger, Rainer; Muñoz, Diego; Hernquist, Lars

doi:10.48550/arxiv.2203.02514

Cited by 3 publications

(5 citation statements)

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“…( 7) (see below). But in some cases, it can also become apsidally locked relative to the binary's eccentricity vector, as found in the 0.2 < ∼ e b < ∼ 0.4 equal-mass binary simulations of Miranda et al (2017) and in the unequal-mass eccentric binary simulations of Siwek et al (2022). An example of the coherent precession of a CBD and its correspondence to a lopsided cavity is illustrated in Figure 6.…”

Section: Disk Eccentricity and Precessionmentioning

confidence: 77%

“…In this section, we summarize the key findings from recent simulations. Our discussion will be guided by our own simulation results using AREPO (Muñoz & Lai 2016, Muñoz et al 2019, Siwek et al 2022) and related work using PLUTO (Miranda et al 2017), but we will compare with the results from other simulations when relevant, and discuss more recent progress. AREPO (Springel 2010, Pakmor et al 2016) is a quasi-Lagrangian Godunov-type moving-mesh code.…”

Section: Simulations Of Circumbinary Accretion: Key Resultsmentioning

confidence: 99%

“…Simulations show that the disk generally exhibits apsidal precession, but the precession rate may not be constant and the line of apses can vary with r. In analogy to test particle orbit, the CBD should evolve according to coexisting "free" and "forced" modes (e.g., see Lubow 2022). In some cases, the CBD can lock onto the binary and stop precessing altogether (Miranda et al 2017, Siwek et al 2022.…”

Section: Disk Eccentricity and Precessionmentioning

confidence: 99%

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Circumbinary Accretion: From Binary Stars to Massive Binary Black Holes

Dong¹,

Muñoz²

2022

Preprint

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We review recent works on the dynamics of circumbinary accretion, including time variability, angular momentum transfer between the disk and the binary, and the secular evolution of accreting binaries. These dynamics can impact stellar binary formation/evolution, circumbinary planet formation/migration, and the evolution of (super)massive black-hole binaries. We discuss the dynamics and evolution of inclined/warped circumbinary disks and connect with recent observations of protoplanetary disks. A special kind of circumbinary accretion involves binaries embedded in "big" disks, which may contribute to the mergers of stellar-mass black holes in AGN disks. Highlights include: Circumbinary accretion is highly variable, being modulated at P b (the binary period) or ∼ 5Pp, depending on the binary eccentricity e b and mass ratio q b . The inner region of the circumbinary disk can develop coherent eccentric structure, which may modulate the accretion and affect the physical processes (e.g. planet migration) taking place in the disk. Over long timescales, circumbinary accretion steers binaries toward equal masses, and it does not always lead to binary orbital decay, as is commonly assumed. The secular orbital evolution depends on the binary parameters (e b and q b ), and on the thermodynamic properties of the accreting gas. A misaligned disk around a low-eccentricity binary tends to evolve toward coplanarity due to viscous dissipation. But when e b is significant, the disk can evolve toward "polar alignment", with the disk plane perpendicular to the binary plane.

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Section: Disk Eccentricity and Precessionmentioning

confidence: 77%

Section: Simulations Of Circumbinary Accretion: Key Resultsmentioning

confidence: 99%

Section: Disk Eccentricity and Precessionmentioning

confidence: 99%

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Circumbinary Accretion: From Binary Stars to Massive Binary Black Holes

Dong¹,

Muñoz²

2022

Preprint

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“…In the litterature the lump, as an overdensity feature, is less visible for eccentric binaries although the symmetry-breaking still occurs for equal-mass binaries (see e.g. Mösta et al 2019, Ragusa et al 2021, Siwek et al 2022. Nonetheless, a vortensity extremum is reported in Mösta et al (2019) for an eccentricity parameter of 0.6, suggesting that even in this case, the RWI could be responsible for the symmetry breaking.…”

Section: Discussionmentioning

confidence: 93%

On the origin of the lump in circumbinary discs

Mignon-Risse,

Varniere,

Casse

2023

Preprint

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Accreting binary black holes (BBHs) are multi-messenger sources, emitting copious electromagnetic (EM) and gravitational waves. One of their most promising EM signatures is the lightcurve modulation caused by a strong, unique and extended azimuthal overdensity structure orbiting at the inner edge of the circumbinary disc (CBD), dubbed 'lump'. In this paper, we investigate the origin of this structure using 2D general-relativistic (GR) hydrodynamical simulations of a CBD in an approximate BBH spacetime. First, we use the symmetric mass-ratio case to study the transition from the natural 𝑚 = 2 mode to 𝑚 = 1. The asymmetry with respect to 𝑚 = 2 grows exponentially, pointing to an instability origin. We indeed find that the CBD edge is prone to a (magneto-)hydrodynamical instability owing to the disc edge density sharpness: the Rossby Wave Instability (RWI). The RWI criterion is naturally fullfilled at the CBD edge and we report the presence of vortices, which are typical structures of the RWI. The RWI is also at work in the asymmetric mass-ratio cases (from 0.1 to 0.5). However, the CBD edge sharpness decreases with a decreasing mass ratio, and so the lump. By proposing a scenario for this lump formation, our work further supports its existence in astrophysical CBDs and potential source for an EM signature of BBHs. Finally, because the RWI is not caused by GR effects, it is also a robust candidate for the lump origin in CBDs around non-compact objects, e.g. binary protostars.

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“…Simulations have been carried out that explore circumbinary disc eccentricity evolution involving eccentric orbit binaries (e.g., Miranda et al 2017). Recently, Siwek et al (2022) analyzed circumbinary disc eccentricity evolution using 2D simulations that covered a set of binary mass ratios and eccentricities. The results show disc eccentricity phase locking at large angles relative to the binary eccentricity, as we find here near resonances.…”

Section: Discussionmentioning

confidence: 99%

Forced Eccentricity in Circumbinary Discs

Lubow¹

2022

Preprint

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We analyze the eccentric response of a low mass coplanar circumbinary disc to secular tidal forcing by a Keplerian eccentric orbit central binary. The disc acquires a forced eccentricity whose magnitude depends on the properties of the binary and disc. The largest eccentricities occur when there is a global apsidal resonance in the disc. The driving frequency by the binary is its apsidal frequency that is equal to zero. A global resonance occurs when the disc properties permit the existence of a zero apsidal frequency free eccentric mode. Resonances occur for different free eccentric modes that differ in the number of radial nodes. For a disc not at resonance, the eccentricity distribution has somewhat similar form to the eccentricity distributions in discs at resonance that have the closest matching disc aspect ratios. For higher disc aspect ratios, the forced eccentricity distribution in a 2D disc is similar to that of the fundamental free mode. The forced eccentricity distribution in a 3D disc is similar to that of higher order free modes, not the fundamental mode, unless the disc is very cool. For parameters close to resonance, large phase shifts occur between the disc and binary eccentricities that are locked in phase. Forced eccentricity may play an important role in the evolution of circumbinary discs and their central binaries.

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Preferential Accretion and Circumbinary Disk Precession in Eccentric Binary Systems

Cited by 3 publications

References 33 publications

Circumbinary Accretion: From Binary Stars to Massive Binary Black Holes

Circumbinary Accretion: From Binary Stars to Massive Binary Black Holes

On the origin of the lump in circumbinary discs

Forced Eccentricity in Circumbinary Discs

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