Numerical Models of Spin-Orbital Coupling in Neutron Star Binaries

TL;DR

This paper introduces a new numerical method for modeling spinning binary neutron stars in quasiequilibrium, capturing spin effects on gravitational and electromagnetic signals during inspiral.

Contribution

It develops a novel numerical scheme for initial data of spinning neutron star binaries, enabling detailed analysis of spin effects in gravitational waveforms and electromagnetic signals.

Findings

Spin angular frequency varies along binary sequences.

Spin effects influence gravitational waveforms.

Electromagnetic signals can reveal neutron star spins.

Abstract

We present a new numerical scheme for solving the initial value problem for quasiequilibrium binary neutron stars allowing for arbitrary spins. We construct sequences of circular-orbit binaries of varying separation, keeping the rest mass and circulation constant along each sequence. The spin angular frequency of the stars is shown to vary along the sequence, a result that can be derived analytically in the PPN limit. This spin effect, in addition to leaving an imprint on the gravitational waveform emitted during binary inspiral, is measurable in the electromagnetic signal if one of the stars is a pulsar visible from Earth.