脉冲星计时中内在的与观测诱导的自旋非平稳性
Intrinsic versus observation induced spin nonstationarity in pulsar timing
- Max Planck Institute for Gravitational Physics (Albert Einstein Institute)（马克斯·普朗克引力物理研究所（爱因斯坦研究所））
- Leibniz Universität Hannover（汉诺威莱布尼茨大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本文提出高斯过程方法，利用脉冲星计时相位数据检验中子星自旋噪声平稳性，区分内在与观测诱导效应，并证明仅观测壳层时模型难以区分，但超流体惯性分数可提供可检验预测。
AI中文摘要：
在中子星的两分量模型中，自旋噪声是否平稳，取决于恒星角动量是在内部守恒，还是通过与壳层和超流体上的独立随机力矩进行外部交换。该问题是在两个分量的角速度中提出的，但射电脉冲星计时仅通过拟合确定性计时模型后的旋转相位来观测壳层。我们开发了一种高斯过程方法，直接用此类相位数据检验自旋噪声的平稳性。从奇异的非平稳和最小的平稳两分量模型的精确解析相位均值和协方差出发，我们证明壳层相位协方差是半可分的，并构建了一个似然函数，其随观测次数线性增长，且计时模型被解析地边缘化。我们使用全状态和仅壳层观测，以及微分后的局部自旋频率，分析了来自两种模型的模拟相位数据。积分、计时模型去除和微分既不会产生也不会消除平稳与非平稳自旋噪声之间的区别，但决定了在有限且含噪声的数据集中有多少区别得以保留。当两个分量都被观测时，模型被明确区分，生成参数被恢复。仅观测壳层时，在大部分参数空间中，两种模型对观测相位的描述同样好，贝叶斯因子约为1且受先验限制。然而，最小模型通过一个由超流体惯性分数设定的单一因子，将隐藏的超流体相位与观测到的壳层相位联系起来，因此对该分数的独立估计（如从滑移中获得的）将其转化为一个可证伪的预测，内部连续引力波观测可以检验该预测。
英文摘要：
Whether spin noise of a neutron star is stationary is, in two-component models, a question of whether stellar angular momentum is conserved internally or exchanged externally through independent stochastic torques on the crust and superfluid. The question is posed in the two components' angular velocities, but radio pulsar timing observes only the crust, through its rotational phase after a deterministic timing model is fitted. We develop a Gaussian process method for testing spin noise stationarity directly with such phase data. Starting from the exact analytical phase means and covariances of a singular, nonstationary and a minimal, stationary two-component model, we show that the crust phase covariances are semiseparable and construct a likelihood that scales linearly with the number of observations, with the timing model marginalized analytically. We analyze simulated phase data from both models using full-state and crust-only observations, and after differentiation into local spin frequencies. Integration, timing model removal and differentiation neither create nor destroy the distinction between stationary and nonstationary spin noise, but determine how much survives in a finite, noisy data set. With both components observed, the models are distinguished decisively and the generating parameters are recovered. With the crust alone, both models describe the observed phase equally well over much of parameter space, and the Bayes factors are of order unity and prior-limited. The minimal model nonetheless ties the hidden superfluid phase to the observed crust phase through a single factor set by the superfluid inertia fraction, so an independent estimate of this fraction, as from glitches, turns it into a falsifiable prediction that a continuous gravitational wave observation of the interior could test.
