Pulsar Timing Array Experiments

TL;DR

Pulsar timing arrays utilize the precise timing of neutron stars to detect low-frequency gravitational waves, offering a complementary approach to existing detectors and potentially revealing signals from supermassive black-hole binaries.

Contribution

This chapter provides an overview of pulsar timing methodology, current PTA efforts, and their potential to detect gravitational waves from supermassive black-hole binaries.

Findings

PTAs are sensitive to nanohertz gravitational waves.

Current efforts are close to detecting a cosmological GW background.

PTAs may also detect continuous waves from individual supermassive black-hole binaries.

Abstract

Pulsar timing is a technique that uses the highly stable spin periods of neutron stars to investigate a wide range of topics in physics and astrophysics. Pulsar timing arrays (PTAs) use sets of extremely well-timed pulsars as a Galaxy-scale detector with arms extending between Earth and each pulsar in the array. These challenging experiments look for correlated deviations in the pulsars' timing that are caused by low-frequency gravitational waves (GWs) traversing our Galaxy. PTAs are particularly sensitive to GWs at nanohertz frequencies, which makes them complementary to other space- and ground-based detectors. In this chapter, we will describe the methodology behind pulsar timing; provide an overview of the potential uses of PTAs; and summarise where current PTA-based detection efforts stand. Most predictions expect PTAs to successfully detect a cosmological background of GWs emitted by supermassive black-hole binaries and also potentially detect continuous-wave emission from binary supermassive black holes, within the next several years.