Gravitational waveforms in scalar-tensor gravity at 2PN relative order

TL;DR

This paper calculates gravitational waveforms in scalar-tensor gravity at 2PN order, focusing on non-spinning, quasi-circular binaries, and compares dipolar and quadrupolar radiation effects relevant for various astrophysical sources.

Contribution

It provides the first detailed 2PN order waveform calculations in scalar-tensor gravity for non-spinning binaries on quasi-circular orbits, including dipolar and quadrupolar radiation effects.

Findings

Dipolar radiation is subdominant due to observational constraints.

Waveforms are computed for both dipolar and quadrupolar driven inspirals.

Results are relevant for current and future gravitational-wave detectors.

Abstract

We compute the gravitational waveform from a binary system in scalar-tensor gravity at 2PN relative order. We restrict our calculation to non-spinning binary systems on quasi-circular orbits and compute the spin-weighted spherical modes of the radiation. The evolution of the phase of the waveform is computed in the time and frequency domains. The emission of dipolar radiation is the lowest-order dissipative process in scalar-tensor gravity. However, stringent constraints set by current astrophysical observations indicate that this effect is subdominant to quadrupolar radiation for most prospective gravitational-wave sources. We compute the waveform for systems whose inspiral is driven by: (a) dipolar radiation (e.g., binary pulsars or spontaneously scalarized systems) and (b) quadrupolar radiation (e.g., typical sources for space-based and ground-based detectors).