The relativistic pulsar-white dwarf binary PSR J1738+0333 - II. The most stringent test of scalar-tensor gravity

Abstract

We report the results of a 10‐year timing campaign on PSR J1738+0333, a 5.85‐ms pulsar in a low‐eccentricity 8.5‐h orbit with a low‐mass white dwarf companion. We obtained 17 376 pulse times of arrival with a stated uncertainty smaller than s and weighted residual rms of s. The large number and precision of these measurements allow highly significant estimates of the proper motion μα, δ= (+7.037 ± 0.005, +5.073 ± 0.012) mas yr−1, parallax πx = (0.68 ± 0.05) mas and a measurement of the apparent orbital decay, (all 1σ uncertainties). The measurements of μα, δ and πx allow for a precise subtraction of the kinematic contribution to the observed orbital decay; this results in a significant measurement of the intrinsic orbital decay: . This is consistent with the orbital decay from the emission of gravitational waves predicted by general relativity, , i.e. general relativity passes the test represented by the orbital decay of this system. This agreement introduces a tight upper limit on dipolar gravitational wave emission, a prediction of most alternative theories of gravity for asymmetric binary systems such as this. We use this limit to derive the most stringent constraints ever on a wide class of gravity theories, where gravity involves a scalar‐field contribution. When considering general scalar–tensor theories of gravity, our new bounds are more stringent than the best current Solar system limits over most of the parameter space, and constrain the matter–scalar coupling constant to be below the 10−5 level. For the special case of the Jordan–Fierz–Brans–Dicke, we obtain the 1σ bound , which is within a factor of 2 of the Cassini limit. We also use our limit on dipolar gravitational wave emission to constrain a wide class of theories of gravity which are based on a generalization of Bekenstein’s Tensor–Vector–Scalar gravity, a relativistic formulation of modified Newtonian dynamics.

Universal I-Q relations for rapidly rotating neutron and strange stars in scalar-tensor theories

“…The general idea behind the scalarization is that for certain ranges of the parameters new solutions with nontrivial scalar field can exist in addition to the pure GR solutions, and the scalarized neutron stars are energetically more favorable compared to their GR counterpart. The current observations of binary pulsars set tight constraints on the coupling parameter in this scalar-tensor theory and for the nonrotating case the scalarized solutions differ only slightly from the general relativistic ones [4,29,30]. But as the results in [25] show, the rotation can enhance the effect of the scalar field considerably and leads to much more significant deviations from GR.…”

Dark matter relic density in scalar-tensor gravity revisited

“…A(ϕ * ) = e 1 2 βϕ 2 * . In this work the authors perform a full numerical integration of 8 Additionally, for the quadratic scalar coupling A(ϕ * ) = e 1 2 βϕ 2 * considered here, the decay of the orbital period of pulsars in asymmetric binaries implies that the coupling parameter β −4.5 [36]. the scalar field evolution equation and calculate the resulting light element abundances using an up-to-date BBN code.…”

Single-pulse and profile-variability study of PSR J1022+1001

“…The pulsar is in a binary with a 7.8-day orbital period with a white dwarf companion, and is thus a potential laboratory for testing the Strong Equivalence Principle (e.g. Freire et al 2012;Antoniadis et al 2013). The integrated pulsed profile of the pulsar consists of a doublepeaked structure at L-band frequencies with a highly linearly polarised trailing component.…”