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

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 $1.04\pm 0.06$ 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 (${\alpha }_0^2\approx 10^{-5}$).

4 pages, 2 figures, To Appear in Physical Review D