Self-consistency of relativistic observables with general relativity in the white dwarf-neutron star binary PSR J1141-6545

Here we report timing measurements of the relativistic binary PSR J1141 - 6545 that constrain the component masses and demonstrate that the orbital period derivative P-b = (-4 +/- 1) x 10(-13) is consistent with gravitational wave emission as described by the general theory of relativity. The mass of the neutron star and its companion are 1.30 +/- 0.02 and 0.986 +/- 0.02 M-., respectively, suggesting a white dwarf companion and extending the range of systems for which general relativity provides a correct description. On evolutionary grounds, the progenitor mass of PSR J1141 - 6545 should be near the minimum for neutron star production. Its mass is 2 standard deviations below the mean of the other neutron stars, suggesting a relationship between progenitor and remnant masses.