Multi-messenger approaches to binary supermassive black holes in the "continuous-wave" regime

TL;DR

This paper reviews the potential of multi-messenger astronomy combining pulsar timing and electromagnetic observations to detect and study supermassive black hole binaries in the gravitational wave 'continuous-wave' regime, enhancing understanding of galaxy evolution.

Contribution

It discusses the prospects and scientific goals of joint electromagnetic and pulsar timing studies for supermassive black hole binaries, emphasizing upcoming observational capabilities.

Findings

High-precision timing arrays can detect gravitational waves from SMBH binaries.

Electromagnetic observations can help identify galactic hosts of gravitational wave sources.

Multi-messenger approaches will advance understanding of galaxy mergers and SMBH evolution.

Abstract

Pulsar timing arrays are sensitive to gravitational waves from supermassive black hole (SMBH) binaries at orbital separations of << 1pc. There is currently an observational paucity of such systems, although they are central figures in studies of galaxy evolution, merger dynamics, and active nucleus formation. We review the prospects of detecting SMBH binaries through electromagnetic radiative processes thought to be associated with galaxy mergers and late-stage binary evolution. We then discuss the scientific goals of joint pulsar timing and electromagnetic studies of these systems, including the facilitation of binary parameter estimation, identifying galactic hosts of gravitational wave emitters, and relevant studies of merger dynamics and cosmology. The use of upcoming high-precision timing arrays with the International Pulsar Timing Array and the Square Kilometre Array, combined with ongoing electromagnetic observing campaigns to identify active SMBH binaries, provide generous possibilities for multi-messenger astrophysics in the near future.