[Paper Review] Sinusoidal Gravitational Waves from the Nuclei of Active Galaxies

Giacomo Giampieri|arXiv (Cornell University)|May 26, 1993

Pulsars and Gravitational Waves Research3 citations

TL;DR

This paper investigates supermassive black hole binaries in active galactic nuclei as sources of detectable sinusoidal gravitational waves, modeling their evolution under simultaneous accretion and gravitational wave emission. It finds that such binaries can emit strong, modulated gravitational wave signals due to mass accretion and orbital decay, making them prime candidates for future space-based gravitational wave observatories like LISA.

ABSTRACT

It is believed that most quasars and galaxies present two common features: the presence in their core of a supermassive object, and the experience of one or more encounters with other galaxies. In this scenario, it is likely that a substantial fraction of active galactic nuclei harbour a supermassive binary, fueled by an accretion disk. These binaries would certainly be among the strongest sources of sinusoidal gravitational waves. We investigate their evolution considering, simultaneously, the accretion of the black hole's masses from the disk, and the gravitational waves emitted during the orbital motion. We also consider other astrophysical scenarios involving a coalescing binary with non constant masses.

Motivation & Objective

• To assess the potential of active galactic nuclei hosting supermassive black hole binaries as sources of detectable gravitational waves.
• To model the coupled evolution of binary black holes under accretion and gravitational wave emission.
• To determine the characteristics of the resulting gravitational wave signals, particularly their sinusoidal modulation.
• To evaluate the detectability of such signals in the context of future space-based gravitational wave observatories.
• To explore the implications of non-constant binary masses due to accretion on wave emission properties.

Proposed method

• Modeling the orbital evolution of a supermassive binary black hole system in an active galactic nucleus.
• Simultaneously solving for mass accretion from a surrounding accretion disk and gravitational wave emission via quadrupole radiation.
• Using a system of coupled differential equations to describe mass growth and orbital decay.
• Applying energy and angular momentum balance to track changes in orbital separation and frequency.
• Considering the effects of non-constant mass evolution on the gravitational wave frequency and amplitude.
• Estimating the gravitational wave strain amplitude and frequency modulation over time.

Experimental results

Research questions

• RQ1 Can supermassive black hole binaries in active galactic nuclei produce detectable sinusoidal gravitational wave signals?
• RQ2 How does ongoing accretion affect the orbital evolution and gravitational wave emission of a binary black hole system?
• RQ3 What is the expected amplitude and frequency modulation of gravitational waves from such systems?
• RQ4 How do non-constant masses influence the waveforms and detectability of gravitational radiation?
• RQ5 What fraction of active galactic nuclei might host binaries capable of emitting strong, observable gravitational waves?

Key findings

• Supermassive binary black holes in active galactic nuclei are likely to be strong sources of sinusoidal gravitational waves due to their high masses and orbital motion.
• Accretion of mass from the disk leads to a continuous increase in binary mass, which modulates the gravitational wave frequency and amplitude.
• The combined effects of mass accretion and gravitational wave emission result in a characteristic chirp-like signal with a non-monotonic frequency evolution.
• The gravitational wave strain amplitude is expected to be significant, potentially detectable by future space-based interferometers like LISA.
• The model predicts that such binaries can emit coherent, sinusoidal gravitational wave signals over long timescales, enhancing their detectability.
• The system's evolution is governed by a balance between mass accretion and energy loss via gravitational radiation, leading to a complex but observable wave signature.