An independent test on the local position invariance of gravity with the triple pulsar PSR J0337+1715

Understand

We design a direct test of the local position invariance (LPI) in the post-Newtonian gravity, using the timing observation of the triple pulsar, PSR J0337+1715.

• The test takes advantage of the large gravitational acceleration exerted by the outer white dwarf to the inner neutron star -- white dwarf binary.
• Using machine-precision three-body simulations and dedicated Markov-chain Monte Carlo (MCMC) techniques with various sampling strategies and noise realizations, we estimate that the Whitehead's parameter could have already been limited to $|\xi| \lesssim 0.4$ (95\% CL), with the published timing data spanning from January 2012 to May 2013.
• The constraint is still orders of magnitude looser than the best limit, yet it is able to independently falsify Whitehead's gravity theory where $\xi=1$.