Gravitational wave sources in the era of multi-frequency gravitational wave astronomy

TL;DR

This paper discusses the diverse sources of gravitational waves across multiple frequency bands, emphasizing their potential to revolutionize our understanding of cosmic phenomena from stellar evolution to the early universe.

Contribution

It provides a comprehensive overview of prospective gravitational wave sources across different frequencies and highlights their scientific significance and expected signals.

Findings

Identification of key gravitational wave sources across frequency bands

Potential insights into star and black hole formation and evolution

Implications for understanding fundamental physics and the early universe

Abstract

The focus of this Chapter is on describing the prospective sources of the gravitational wave universe accessible to present and future observations, from kHz, to mHz down to nano-Hz frequencies. The multi-frequency gravitational wave universe gives a deep view into the cosmos, inaccessible otherwise. It has as main actors core-collapsing massive stars, neutron stars, coalescing compact object binaries of different flavours and stellar origin, coalescing massive black hole binaries, extreme mass ratio inspirals, and possibly the very early universe itself. Here, we highlight the science aims and describe the gravitational wave signals expected from the sources and the information gathered in it. We show that the observation of gravitational wave sources will play a transformative role in our understanding of the processes ruling the formation and evolution of stars and black holes, galaxy clustering and evolution, the nature of the strong forces in neutron star interiors, and the most mysterious interaction of Nature: gravity. The discovery, by the LIGO Scientific Collaboration and Virgo Collaboration, of the first source of gravitational waves from the cosmos GW150914, and the superb technological achievement of the space mission LISA Pathfinder herald the beginning of the new phase of exploration of the universe.