Discovery of Three Wide‐Orbit Binary Pulsars: Implications for Binary Evolution and Equivalence Principles

We report the discovery of three binary millisecond pulsars during the ParkesMultibeam Pulsar Survey of the Galactic Plane. The objects are highly recycledand are in orbits of many tens of days about low-mass white-dwarf companions.The eccentricity of one object, PSR J1853+1303, is more than an order ofmagnitude lower than predicted by the theory of convective fluctuations duringtidal circularization. We demonstrate that, under the assumption that thesystems are randomly oriented, current theoretical models of thecore-mass--orbital-period relation for the progenitors of these systems likelyoverestimate the white-dwarf masses, strengthening previous concerns about thematch of these models to the data. The new objects allow us to update thelimits on violation of relativistic equivalence principles to 95% confidenceupper limits of 5.6 x 10^-3 for the Strong Equivalence Principle parameterDelta and 4.0 x 10^-20 for the Lorentz-invariance/momentum-conservationparameter alpha_3.Comment: 8 pages; accepted to ApJ. Small changes to parameters from including correct Parkes clock corrections; changes/corrections to Figures 1, 4 and 5; minor changes to text and references. The limit on Delta has increased from 0.0055 to 0.005