A tighter test of the local Lorentz invariance of gravity using PSR J2317-1439

Gravity being a long-range force, one might a priori expect the universe's global matter distribution to select a preferred rest frame for local gravitational physics. The phenomenology of preferred-frame effects, in the strong-gravitational field context of binary pulsars, is described by two parameters, alpha(1), and alpha(2). These parameters vanish identically in general relativity and reduce, in the weak-field limit, to the two parameterized post-Newtonian (PPN) parameters alpha(1) and alpha(2). We derive a limit of \alpha(1)\ < 1.7 x 10(-4) (90% C.L.) using the very low eccentricity binary pulsar PSR J2317 +/- 1439, improving by a factor of 3 on previous limits.