Continued timing observations of the double pulsar PSR J0737–3039A/B, which consists of two active radio pulsars (A and B) that orbit each other with a period of 2.45 h in a mildly eccentric ($e=0.088$) binary system, have led to large improvements in the measurement of relativistic effects in this system. With a 16-yr data span, the results enable precision tests of theories of gravity for strongly self-gravitating bodies and also reveal new relativistic effects that have been expected but are now observed for the first time. These include effects of light propagation in strong gravitational fields which are currently not testable by any other method. In particular, we observe the effects of retardation and aberrational light bending that allow determination of the spin direction of the pulsar. In total, we detect seven post-Keplerian parameters in this system, more than for any other known binary pulsar. For some of these effects, the measurement precision is now so high that for the first time we have to take higher-order contributions into account. These include the contribution of the A pulsar’s effective mass loss (due to spin-down) to the observed orbital period decay, a relativistic deformation of the orbit, and the effects of the equation of state of superdense matter on the observed post-Keplerian parameters via relativistic spin-orbit coupling. We discuss the implications of our findings, including those for the moment of inertia of neutron stars, and present the currently most precise test of general relativity’s quadrupolar description of gravitational waves, validating the prediction of general relativity at a level of $1.3\times {10}^{-4}$ with 95% confidence. We demonstrate the utility of the double pulsar for tests of alternative theories of gravity by focusing on two specific examples and also discuss some implications of the observations for studies of the interstellar medium and models for the formation of the double pulsar system. Finally, we provide context to other types of related experiments and prospects for the future.

中文翻译：

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双脉冲星的强场重力测试

对双脉冲星 PSR J0737-3039A/B 的持续计时观测，它由两颗活跃的射电脉冲星（A 和 B）组成，它们以 2.45 小时的周期在轻度偏心（$\mathrm{电子}=0.088$) 二元系统，导致该系统中相对论效应的测量有了很大的改进。凭借 16 年的数据跨度，该结果能够对强自引力天体的引力理论进行精确测试，并且还揭示了预期但现在首次被观察到的新的相对论效应。这些包括光在强引力场中传播的影响，目前无法通过任何其他方法进行测试。特别是，我们观察了延迟和像差光弯曲的影响，它们可以确定脉冲星的自旋方向。总的来说，我们在这个系统中检测到七个后开普勒参数，比任何其他已知的双脉冲星都要多。对于其中一些影响，测量精度现在如此之高，以至于我们第一次必须考虑高阶贡献。这些包括 A 脉冲星的有效质量损失（由于自旋下降）对观测到的轨道周期衰减的贡献、轨道的相对论变形，以及超密物质状态方程对观测到的后开普勒参数的影响通过相对论自旋轨道耦合。我们讨论了我们发现的意义，包括对中子星转动惯量的意义，并提出了目前对广义相对论引力波四极描述的最精确测试，在一个水平上验证广义相对论的预测 轨道的相对论变形，以及超稠密物质状态方程通过相对论自旋轨道耦合对观测到的开普勒后参数的影响。我们讨论了我们发现的意义，包括对中子星转动惯量的意义，并提出了目前对广义相对论引力波四极描述的最精确测试，在一个水平上验证广义相对论的预测 轨道的相对论变形，以及超稠密物质状态方程通过相对论自旋轨道耦合对观测到的开普勒后参数的影响。我们讨论了我们发现的意义，包括对中子星转动惯量的意义，并提出了目前对广义相对论引力波四极描述的最精确测试，在一个水平上验证广义相对论的预测$1.3\times {10}^{-4}$有 95% 的置信度。我们通过关注两个具体例子来证明双脉冲星在测试替代引力理论中的效用，并讨论了观测对星际介质研究和双脉冲星系统形成模型的一些影响。最后，我们为其他类型的相关实验和未来前景提供了背景。