Pulsar timing arrays provide a unique means to detect nanohertz gravitational waves through long-term measurements of pulse arrival times from an ensemble of millisecond pulsars. After years of observations, some timing array pulsars have been shown to be dominated by low-frequency red noise, including spin noise that might be associated with pulsar rotational irregularities. The power spectral density of pulsar timing red noise is usually modeled with a power law or a power law with a turnover frequency below which the noise power spectrum plateaus. If there is a turnover in the spin noise of millisecond pulsars, residing within the observation band of current and/or future pulsar timing measurements, it may be easier than projected to resolve the gravitational-wave background from supermassive binary black holes. Additionally, the spectral turnover can provide valuable insights on neutron star physics. In the recent study by Melatos and Link, the authors provided a derivation of the model for power spectral density of spin noise from superfluid turbulence in the core of a neutron star, from first principles. The model features a spectral turnover, which depends on the dynamical response time of the superfluid and the steady-state angular velocity lag between the crust and the core of the star. In this work, we search for a spectral turnover in spin noise using the first data release of the International Pulsar Timing Array. Through Bayesian model selection, we find no evidence of a spectral turnover. Our analysis also shows that data from pulsars J1939+2134, J1024$-$0719 and J1713+0747 prefers the power-law model to the superfluid turbulence model.

中文翻译：

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毫秒脉冲星的自旋噪声是否存在光谱翻转？

脉冲星定时阵列提供了一种独特的方法，通过长期测量来自毫秒脉冲星集合的脉冲到达时间来检测纳赫兹引力波。经过多年的观察，一些定时阵列脉冲星已被证明以低频红噪声为主，包括可能与脉冲星旋转不规则相关的自旋噪声。脉冲星定时红噪声的功率谱密度通常用幂律或具有周转频率的幂律建模，低于该周转频率噪声功率谱平稳。如果位于当前和/或未来脉冲星计时测量的观测带内的毫秒脉冲星的自旋噪声发生翻转，那么解析来自超大质量双黑洞的引力波背景可能比预计的更容易。此外，光谱转换可以为中子星物理学提供有价值的见解。在 Melatos 和 Link 最近的研究中，作者根据第一原理推导了中子星核心超流体湍流自旋噪声功率谱密度模型。该模型具有光谱翻转，这取决于超流体的动力学响应时间和地壳与恒星核心之间的稳态角速度滞后。在这项工作中，我们使用国际脉冲星定时阵列的第一个数据发布来搜索自旋噪声中的光谱转换。通过贝叶斯模型选择，我们没有发现光谱转换的证据。我们的分析还表明，脉冲星 J1939+2134、J1024$-$0719 和 J1713+0747 的数据更喜欢幂律模型而不是超流体湍流模型。