Nonlinear Orbital Variations in Binary Radio Pulsars from Lense-Thirring Precession

TL;DR

This paper demonstrates that nonlinear orbital variations caused by Lense-Thirring precession in binary pulsars can be used to measure the pulsar's moment of inertia, providing a new method to analyze pulsar timing data.

Contribution

The work shows that nonlinear orbital variations due to LT precession are detectable and can constrain pulsar moment of inertia without relying on timing-independent measurements.

Findings

Nonlinear orbital variations are detectable with current pulsar timing precision.

Simulations indicate detection is possible in PSR J1757-1854 after 15 years.

Nonlinear signatures help isolate LT precession effects from other mechanisms.

Abstract

A future measurement of Lense-Thirring (LT) precession using a binary radio pulsar is expected to yield the pulsar's moment of inertia ($I_{\rm p}$). However, most of the known pulsar-binary systems expected to provide this opportunity will exhibit linear variations in the orbital elements due to LT precession that are difficult to separate from variations induced by other mechanisms. In this work, we demonstrate that the pulsar-timing signature of LT precession for an arbitrary orbital orientation produces nonlinear orbital variations; if detected, these nonlinear variations provide a means to constrain $I_{\rm p}$ without the need for timing-independent measurements of orbital geometry or distance. We show through simulations that these signatures are indeed detectable in pulsar-binary systems with an appropriate combination of timing precision and orbital geometry. Our simulations also show that nonlinear orbital variations from LT precession are expected to be detectable in PSR J1757$-$1854 after only 15 yr of dedicated timing.