2015ApJ...809...41Z

We report 21-year timing of one of the most precise pulsars: PSR J1713+0747. Its pulse times of arrival are well modeled by a comprehensive pulsar binary model including its three-dimensional orbit and a noise model that incorporates short- and long-timescale correlated noise such as jitter and red noise. Its timing residuals have weighted root mean square ∼92 ns. The new data set allows us to update and improve previous measurements of the system properties, including the masses of the neutron star (1.31 ± 0.11 M_☉) and the companion white dwarf (0.286 ± 0.012 M_☉) as well as their parallax distance 1.15 ± 0.03 kpc. We measured the intrinsic change in orbital period, {dot}P_b^Int, is -0.20 ± 0.17 ps s^–1, which is not distinguishable from zero. This result, combined with the measured {dot}P_b^Int of other pulsars, can place a generic limit on potential changes in the gravitational constant G. We found that {dot}G/G is consistent with zero [(-0.6 ± 1.1) x 10^–12 yr^–1, 95% confidence] and changes at least a factor of 31 (99.7% confidence) more slowly than the average expansion rate of the universe. This is the best {dot}G/G limit from pulsar binary systems. The {dot}P_b^Int of pulsar binaries can also place limits on the putative coupling constant for dipole gravitational radiation κ_D=(-0.9±3.3)×10^–4 (95% confidence). Finally, the nearly circular orbit of this pulsar binary allows us to constrain statistically the strong-field post-Newtonian parameters Δ, which describes the violation of strong equivalence principle, and 1₃, which describes a breaking of both Lorentz invariance in gravitation and conservation of momentum. We found, at 95% confidence, Δ0.01 and 1₃ 2×10^–20 based on PSR J1713+0747.