Relativistic Spin Precession in the Double Pulsar

TL;DR

The study tests gravity in the strong-field regime by measuring relativistic spin precession of pulsar B in the double pulsar PSR J0737-3039A/B. It develops a dipolar magnetosphere eclipse model, with geometry described by $(\alpha,\theta,\phi)$ and magnetospheric parameters $(\mu, R_{\rm mag}, z_0)$, and uses a line-of-sight optical depth $\tau$ to connect eclipse morphology to spin orientation. Through Bayesian inference on 63 eclipses at 820 MHz, allowing $\phi$ to precess as $\phi=\phi_0-\Omega_B t$, the authors measure $\Omega_B=4.77^{+0.66}_{-0.65}\,^{\circ}{\rm yr}^{-1}$, consistent with the GR prediction $5.0734\pm0.0007\,^{\circ}{\rm yr}^{-1}$ within 13% (68% CL). This provides a robust, strong-field test of gravity and demonstrates the potential for tighter constraints with future radio telescopes (e.g., the SKA).

Abstract

The double pulsar PSR J0737-3039A/B consists of two neutron stars in a highly relativistic orbit that displays a roughly 30-second eclipse when pulsar A passes behind pulsar B. Describing this eclipse of pulsar A as due to absorption occurring in the magnetosphere of pulsar B, we successfully use a simple geometric model to characterize the observed changing eclipse morphology and to measure the relativistic precession of pulsar B's spin axis around the total orbital angular momentum. This provides a test of general relativity and alternative theories of gravity in the strong-field regime. Our measured relativistic spin precession rate of 4.77 (+0.66,-0.65) degrees per year (68% confidence level) is consistent with that predicted by general relativity within an uncertainty of 13%.