Eccentric Minidisks in Accreting Binaries

Westernacher-Schneider, John Ryan; Zrake, Jonathan; MacFadyen, Andrew; Haiman, Zoltán

doi:10.3847/1538-4357/ad1a17

Cited by 5 publications

(2 citation statements)

References 78 publications

(91 reference statements)

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“…The general schema of this project is flexible enough to incorporate other variability models in future work, like the continuous-time autoregressive moving average models (Kelly et al 2014) and the damped harmonic oscillator model (Yu et al 2022). Future work can also include a more detailed consideration of the differences between accretion disks around single quasars with the circumbinary disks and mini-disks in binary quasars (Artymowicz & Lubow 1996;MacFadyen & Milosavljević 2008;Westernacher-Schneider et al 2024).…”

Section: Variability Modelmentioning

confidence: 99%

Reliable Identification of Binary Supermassive Black Holes from Rubin Observatory Time-domain Monitoring

Davis,

Grace,

Trump

et al. 2024

ApJ

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Periodic signatures in time-domain observations of quasars have been used to search for binary supermassive black holes (SMBHs). These searches, across existing time-domain surveys, have produced several hundred candidates. The general stochastic variability of quasars, however, can masquerade as a false-positive periodic signal, especially when monitoring cadence and duration are limited. In this work, we predict the detectability of binary SMBHs in the upcoming Rubin Observatory Legacy Survey of Space and Time (LSST). We apply computationally inexpensive sinusoidal curve fits to millions of simulated LSST Deep Drilling Field light curves of both single, isolated quasars and binary quasars. The period and phase of simulated binary signals can generally be disentangled from quasar variability. Binary amplitude is overestimated and poorly recovered for two-thirds of potential binaries due to quasar accretion variability. Quasars with strong intrinsic variability can obscure a binary signal too much for recovery. We also find that the most luminous quasars mimic current binary candidate light curves and their properties: The false-positive rates are 60% for these quasars. The reliable recovery of binary period and phase for a wide range of input binary LSST light curves is promising for multi-messenger characterization of binary SMBHs. However, pure electromagnetic detections of binaries using photometric periodicity with amplitude greater than 0.1 mag will result in samples that are overwhelmed by false positives. This paper represents an important and computationally inexpensive way forward for understanding the true and false-positive rates for binary candidates identified by Rubin.

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Section: Variability Modelmentioning

confidence: 99%

Reliable Identification of Binary Supermassive Black Holes from Rubin Observatory Time-domain Monitoring

Davis,

Grace,

Trump

et al. 2024

ApJ

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“…Sailfish is a GPUaccelerated version of Mara3 that also includes post-processing modules to synthesize light curves of thermal disk emission. It is the code that was used in Westernacher-Schneider et al (2022), Major Krauth et al (2023), and Westernacher-Schneider et al (2024. Sailfish is very fast (10 9 zone updates per second for this problem on an A100 GPU), and it runs efficiently on multi-GPU nodes.…”

Section: A6 Mara3 and Sailfishmentioning

confidence: 99%

The Santa Barbara Binary−disk Code Comparison

Duffell,

Dittmann,

D’Orazio

et al. 2024

ApJ

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We have performed numerical calculations of a binary interacting with a gas disk, using 11 different numerical methods and a standard binary−disk setup. The goal of this study is to determine whether all codes agree on a numerically converged solution and to determine the necessary resolution for convergence and the number of binary orbits that must be computed to reach an agreed-upon relaxed state of the binary−disk system. We find that all codes can agree on a converged solution (depending on the diagnostic being measured). The zone spacing required for most codes to reach a converged measurement of the torques applied to the binary by the disk is roughly 1% of the binary separation in the vicinity of the binary components. For our disk model to reach a relaxed state, codes must be run for at least 200 binary orbits, corresponding to about a viscous time for our parameters, 0.2(a 2Ω B /ν) binary orbits, where ν is the kinematic viscosity. The largest discrepancies between codes resulted from the dimensionality of the setup (3D vs. 2D disks). We find good agreement in the total torque on the binary between codes, although the partition of this torque between the gravitational torque, orbital accretion torque, and spin accretion torque depends sensitively on the sink prescriptions employed. In agreement with previous studies, we find a modest difference in torques and accretion variability between 2D and 3D disk models. We find cavity precession rates to be appreciably faster in 3D than in 2D.

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Gas assisted binary black hole formation in AGN discs

Whitehead,

Rowan,

Boekholt

et al. 2024

Monthly Notices of the Royal Astronomical Society

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We investigate close encounters by stellar mass black holes (BHs) in the gaseous discs of active galactic nuclei (AGNs) as a potential formation channel of binary black holes (BBHs). We perform a series of 2D isothermal viscous hydrodynamical simulations within a shearing box prescription using the Eulerian grid code Athena++. We co-evolve the embedded BHs with the gas keeping track of the energetic dissipation and torquing of the BBH by gas gravitation and inertial forces. To probe the dependence of capture on the initial conditions, we discuss a suite of 345 simulations spanning BBH impact parameter (b) and local AGN disc density (ρ0). We identify a clear region in b − ρ0 space where gas assisted BBH capture is efficient. We find that the presence of gas leads to strong energetic dissipation during close encounters between unbound BHs, forming stably bound eccentric BBHs. We find that the gas dissipation during close encounters increases for systems with increased disc density and deeper periapsis passages rp, fitting a power law such that $\Delta E \propto \rho _0^{\alpha }r_{\mathrm{p}}^{\beta }$, where {α, β} = {1.01 ± 0.04, −0.43 ± 0.03}. Alternatively, the gas dissipation is approximately ΔE = 4.3MdvHvp, where Md is the mass of a single BH minidisc just prior to the encounter when the binary separation is 2rH (two binary Hill radii), vH and vp are the relative BH velocities at 2rH and at the first closest approach, respectively. We derive a prescription for capture which can be used in semi-analytical models of AGN. We do not find the dissipative dynamics observed in these systems to be in agreement with the simple gas dynamical friction models often used in the literature.

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Eccentric Minidisks in Accreting Binaries

Cited by 5 publications

References 78 publications

Reliable Identification of Binary Supermassive Black Holes from Rubin Observatory Time-domain Monitoring

Reliable Identification of Binary Supermassive Black Holes from Rubin Observatory Time-domain Monitoring

The Santa Barbara Binary−disk Code Comparison

Gas assisted binary black hole formation in AGN discs

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