Electromagnetic signatures of supermassive black hole binaries resolved by PTAs

Abstract

Pulsar timing arrays (PTAs) may eventually be able to detect not only the stochastic gravitational-wave (GW) background of SMBH binaries, but also individual, particularly massive binaries whose signals stick out above the background. In this contribution, we discuss the possibility of identifying and studying such `resolved' binaries through their electromagnetic emission. The host galaxies of such binaries are themselves expected to be also very massive and rare, so that out to redshifts z~2 a unique massive galaxy may be identified as the host. At higher redshifts, the PTA error boxes are larger and may contain as many as several hundred massive-galaxy interlopers. In this case, the true counterpart may be identified, if it is accreting gas efficiently, as an active galactic nucleus (AGN) with a peculiar spectrum and variable emission features. Specifically, the binary's tidal torques expel the gas from the inner part of the accretion disk, making it unusually dim in X-ray and UV bands and in broad optical emission lines. The tails of the broad wings of any FeK-alpha emission line may also be `clipped' and missing. The binary's orbital motion, as well as the gas motions it induces, may trigger quasiperiodic variations. These include coherent flux variability, such as luminous, multi-wavelength flares, as well as Doppler shifts of broad emission lines and `see-saw' oscillations in the FeK-alpha line. Additional features, such as evidence for a recent major merger or dual collimated jets, could also corroborate the counterpart. These properties would make resolved PTA sources stand out among AGN with similar overall luminosities and allow their identification.

18 pages, 5 figures, accepted for publication in a focus issue on PTAs in Classical and Quantum Gravity

References in corpus (17)

• An Observational Determination of the Bolometric Quasar Luminosity Function
• A massive binary black-hole system in OJ287 and a test of general relativity
• Massive black hole binary mergers within sub-pc scale gas discs
• Rapid Formation of Supermassive Black Hole Binaries in Galaxy Mergers with Gas
• The Population of Viscosity- and Gravitational Wave-Driven Supermassive Black Hole Binaries Among Luminous AGN
• Alignment of the spins of supermassive black holes prior to coalescence
• Gravitational waves from resolvable massive black hole binary systems and observations with Pulsar Timing Arrays
• An Over-Massive Black Hole in the Compact Lenticular Galaxy NGC1277
• Measuring the parameters of massive black hole binary systems with Pulsar Timing Array observations of gravitational waves
• Binary Black-Hole Mergers in Magnetized Disks: Simulations in Full General Relativity
• Environmental Dependence of Dark Matter Halo Growth I: Halo Merger Rates
• A supermassive binary black hole with triple disks
• On the masses of OJ287 black holes
• Identifying Decaying Supermassive Black Hole Binaries from their Variable Electromagnetic Emission
• Observable Consequences of Merger-Driven Gaps and Holes in Black Hole Accretion Disks
• Resolving multiple supermassive black hole binaries with pulsar timing arrays II: genetic algorithm implementation
• Search of sub-parsec massive binary black holes through line diagnosis II

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• Accretion disks around binary black holes of unequal mass: GRMHD simulations of postdecoupling and merger
• Detecting triple systems with gravitational wave observations
• Constraining Sub-Parsec Binary Supermassive Black Holes in Quasars with Multi-Epoch Spectroscopy. II. The Population with Kinematically Offset Broad Balmer Emission Lines
• Detection of eccentric supermassive black hole binaries with pulsar timing arrays: Signal-to-noise ratio calculations
• Radio-Selected Binary Active Galactic Nuclei from the Very Large Array Stripe 82 Survey
• Supermassive Black Hole Binaries: The Search Continues
• Accretion and Orbital Inspiral in Gas-Assisted Supermassive Black Hole Binary Mergers
• Infalling clouds onto super-massive black hole binaries - I. Formation of discs, accretion and gas dynamics
• Apparent Superluminality of Lensed Gravitational Waves
• Lighthouse in the Dust: Infrared Echoes of Periodic Emission from Massive Black Hole Binaries
• How bright are the gaps in circumbinary disk systems?
• Pulsar timing arrays and the challenge of massive black hole binary astrophysics
• Spectral Energy Distributions of Candidate Periodically-Variable Quasars: Testing the Binary Black Hole Hypothesis
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• Very Large Array imaging rules out precessing radio jets in three DES$-$SDSS-selected candidate periodic quasars
• Investigating the Accretion Nature of Binary Supermassive Black Hole Candidate SDSS J025214.67-002813.7