Gravitational-radiation losses from the pulsar-white-dwarf binary PSR J1141-6545

TL;DR

This paper presents new timing measurements of the pulsar-white-dwarf binary PSR J1141-6545, confirming gravitational wave emission consistent with general relativity and placing constraints on alternative gravity theories.

Contribution

It provides the first precise measurement of orbital decay in this asymmetric system and constrains tensor-scalar gravity theories more tightly than previous bounds.

Findings

Orbital decay rate matches GR predictions within measurement errors.

Shapiro delay measurements support the derived orbital inclination.

Constraints on scalar-tensor gravity coupling are significantly improved.

Abstract

Pulsars in close binary orbit around another neutron star or a massive white dwarf make ideal laboratories for testing the predictions of gravitational radiation and self-gravitational effects. We report new timing measurements of the pulsar-white-dwarf binary PSR J1141-6545, providing strong evidence that such asymmetric systems have gravitational wave losses that are consistent with general relativity. The orbit is found to be decaying at a rate of $1.04\pm0.06$ times the general relativistic prediction and the Shapiro delay is consistent with the orbital inclination angle derived from scintillation measurements. The system provides a unique test-bed for tensor-scalar theories of gravity; our current measurements place stringent constraints in the theory space, with a limit of $\alpha_0^2 < 2.1 \times 10^{-5}$ for weakly non-linear coupling and an asymptotic limit of $\alpha_0^2 < 3.4 \times 10^{-6}$ for strongly non-linear coupling, where $\alpha_0$ is the linear coupling strength of matter to an underlying scalar field. This asymptotic limit is nearly three times smaller than the Cassini bound ($\alpha_0^2 \approx 10^{-5}$).