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

TL;DR

This paper presents a novel test of local position invariance in gravity using pulsar timing data from a triple system, constraining Whitehead's parameter and independently falsifying a specific gravity theory.

Contribution

It introduces a new method leveraging three-body simulations and MCMC to test LPI with pulsar data, providing an independent constraint on Whitehead's gravity theory.

Findings

Whitehead's parameter constrained to || d7 0.4 at 95% CL

Test independently falsifies Whitehead's gravity where =1

Method is immune to extra assumptions and uses full three-body dynamics

Abstract

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 $\xi=1$. In addition, the new test is immune to extra assumptions and involves full dynamics of a three-body system with a strongly self-gravitating neutron star.