Pulsar timing uses the highly stable pulsar spin period to investigate many astrophysical topics. In particular, pulsar timing arrays make use of a set of extremely well-timed pulsars and their time correlations as a challenging detector of gravitational waves. It turns out that pulsar timing arrays are particularly sensitive to ultra-low-frequency gravitational waves, which makes them complementary to other gravitational-wave detectors. Here, we summarize the basics, focusing especially on supermassive black-hole binaries and cosmic strings, which have the potential to form a stochastic gravitational-wave background in the pulsar timing array detection band, and the scientific goals on this challenging topic. We also briefly outline the recent interesting results of the main pulsar timing array collaborations, which have found strong evidence of a common-spectrum process compatible with a stochastic gravitational-wave background and mention some new perspectives that are particularly interesting in view of the forthcoming radio observatories such as the Five hundred-meter Aperture Spherical Telescope, the MeerKAT telescope, and the Square Kilometer Array.
Even though Pulsar Timing Arrays already have the potential to detect the gravitational wave background by finding a quadrupole correlation in the timing residuals, this goal has not yet been achieved. Motivated by some theoretical arguments, we analyzed some advantages of including the millisecond pulsars within globular clusters, especially those in their cores, in current and future Pulsar Timing Array projects for detecting the gravitational waves emitted by an ensemble of supermassive black holes.
We suggest the possibility of including millisecond pulsars inside the core of globular clusters in pulsar timing array experiments. Since they are very close to each other, their gravitational wave induced timing residuals are expected to be almost the same, because both the Earth and the pulsar terms are correlated. We simulate the expected timing residuals, due to the gravitational wave signal emitted by a uniform supermassive black-hole binary population, on the millisecond pulsars inside a globular cluster core. In this respect, Terzan 5 has been adopted as a globular cluster prototype an…
We aim to resolve a misunderstanding about whether the so-called "Earth term" in the pulsar timing response to a gravitational wave is in phase among a set of pulsars. We note that the misunderstanding has potentially arisen from the statements that the Earth term is "coherent" or "builds up coherently" among the pulsars. We clarify what authors mean by "coherent" in these statements, pointing out that "coherent" does not indicate that the Earth terms are in phase among the pulsars. Using the pulsar timing residuals induced by a continuous gravitational wave, we show that the Earth term does n…
Pulsar timing array signals induced by black hole binaries in relativistic eccentric orbits
非圆轨道上的单个超大质量黑洞双星可能是快速成熟的脉冲星定时阵列实验的纳赫兹引力波源。我们发展了一种精确有效的方法来计算脉冲星定时阵列信号，由于引力波从吸入相对论偏心轨道的超大质量黑洞双星。我们的方法采用开普勒型参数解模型的第三后牛顿精确进动偏心轨道，而一个新的半解析处方提供了模型的四极阶引力波发射的影响。这些输入导致一个半解析的处方来模拟这样的信号，引起的非自旋黑洞二进制沿任意偏心率轨道螺旋。此外，我们提供了一个完整的分析处方模型脉冲星定时阵列信号从黑洞二进制沿适度偏心轨道吸气，Boetzelet等人的影响。[Phys. Rev. D 96，044011（2017）]。这些方法正在被纳入企业和TEMPO 2搜索脉冲星定时阵列数据集中存在这样的二进制文件。
The detection of a stochastic background of low-frequency gravitational waves by pulsar-timing and astrometric surveys will enable tests of gravitational theories beyond general relativity. These theories generally permit gravitational waves with non-Einsteinian polarization modes, which may propagate slower than the speed of light. We use the total-angular-momentum wave formalism to derive the angular correlation patterns of observables relevant for pulsar timing arrays and astrometry that arise from a background of subluminal gravitational waves with scalar, vector, or tensor polarizations. …
