The 2.5PN gravitational wave polarisations from inspiralling compact binaries in circular orbits
K G Arun, Luc Blanchet, Bala R Iyer, Moh'd S S Qusailah
TL;DR
The paper delivers a complete 2.5PN gravitational waveform for inspiralling compact binaries in quasi-circular orbits using the multipolar post-Minkowskian framework, including both instantaneous and hereditary contributions (tails and memory). It extends prior 2PN results to 2.5PN, providing ready-to-use expressions for the plus and cross polarizations and detailing the source multipole moments required, while discussing regularization issues and the role of past history in memory terms. The authors model the past binary evolution with an adiabatic Newtonian inspiral to evaluate memory and tail integrals, and they reformulate the waveform in terms of a phase variable that absorbs logarithmic frequency terms to simplify templates. These results enhance gravitational-wave data analysis for both ground-based detectors (LIGO/VIRGO) and space-based detectors (LISA) by delivering higher-accuracy templates and clarifying the structure of non-linear effects such as memory and tails at this order.
Abstract
Using the multipolar post-Minkowskian and matching formalism we compute the gravitational waveform of inspiralling compact binaries moving in quasi-circular orbits at the second and a half post-Newtonian (2.5PN) approximation to general relativity. The inputs we use include notably the mass-type quadrupole at the 2.5PN order, the mass octupole and current quadrupole at the 2PN order, the mass $2^5$-pole and current $2^4$-pole at 1PN. The non-linear hereditary terms come from the monopole-quadrupole multipole interactions or tails, present at the 1.5PN, 2PN and 2.5PN orders, and the quadrupole-quadrupole interaction arising at the 2.5PN level. In particular, the specific effect of non-linear memory is computed using a simplified model of binary evolution in the past. The ``plus'' and ``cross'' wave polarisations at the 2.5PN order are obtained in ready-to-use form, extending the 2PN results calculated earlier by Blanchet, Iyer, Will and Wiseman.
