Angular Momentum Flux in Scalar-Tensor Theories up to 1.5 post-Newtonian Order

TL;DR

This paper calculates the angular momentum flux in scalar-tensor theories for eccentric binary systems up to 1.5PN order, including tensor and scalar contributions with tail and memory effects, aiding waveform modeling.

Contribution

It provides explicit formulas for angular momentum flux, including tail and memory effects, in scalar-tensor theories up to 1.5PN order, which was not previously available.

Findings

Derived explicit tail effect expressions using Fourier decomposition.

Computed non-linear memory effects for elliptic orbits in scalar-tensor theories.

Enhanced understanding of radiation-reaction forces for eccentric binaries.

Abstract

We compute the angular momentum flux from a non-circular nonspinning binary system of compact objects in massless scalar-tensor theories up to one and a half post-Newtonian (1.5PN) order using multipole moments. The angular momentum flux in scalar-tensor theories involves both a tensorial and a scalar contribution which can be further decomposed as instantaneous, tail and non-linear memory effects up to 1.5PN order. We compute the explicit expressions of tail effects using the Fourier decomposition of tensorial and scalar multipole moments, and non-linear memory effects using the Newtonian order quasi-Keplerian representation of elliptic orbits in scalar-tensor theories. This work is important to construct the radiation-reaction force and hence the waveform templates for eccentric binaries in scalar-tensor theories of gravity.