吸积中子星在力矩平衡附近的自旋游走：对引力波搜索的启示
Spin wandering of an accreting neutron star near torque balance: implications for gravitational wave searches
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中文总结 AI 辅助
本文通过奥恩斯坦-乌伦贝克模型理论推导了吸积中子星自旋游走导致的引力波频率标准差，并预测了相干搜索的最大时间间隔，强调了半相干算法在引力波搜索中的必要性。
中文摘要 AI 辅助
引力辐射反作用与磁离心吸积之间的力矩平衡，是吸积中子星转速低于离心分裂速度的原因之一。吸积盘中的随机过程，如瑞利-泰勒不稳定性和闪烁噪声，会驱动自旋频率$f_\ast$和引力波频率$f_{\rm gw}\propto f_\ast$围绕其力矩平衡值随机游走。本文从理论上，通过理想化的奥恩斯坦-乌伦贝克模型表明，$f_{\rm gw}$的标准差由$\sigma_{f_{\rm gw}}(h_0) \propto f_{\rm gw} h_0 D \beta T^{1/2}$给出，或等价地$\sigma_{f_{\rm gw}}(F_{\rm X}) \propto f_{\rm gw}^{1/2} F_{\rm X}^{1/2} D \beta T^{1/2}$，其中$h_0$是特征波应变，$F_{\rm X}$是X射线通量，$D$是源距离，$\beta$和$T$分别是随机力矩的分数振幅和自相关时间尺度。人们可以利用$\sigma_{f_{\rm gw}}(h_0)$和$\sigma_{f_{\rm gw}}(F_{\rm X})$，通过与观测到的$\sigma_{f_{\rm gw}}$进行比较，来检验引力波搜索中候选探测的物理一致性。自旋游走影响搜索设计，因为它设定了信号可被视为相干的最大时间间隔$\max(T_{\rm coh})$。奥恩斯坦-乌伦贝克计算预测$10^{-1} \lesssim \max(T_{\rm coh}) / (1\\, {\rm day}) \lesssim 10^3$，且$3\times 10^{-2} \lesssim \beta T^{1/2} / (1 \\, {\rm s^{1/2}} ) \lesssim 4$，适用于瑞利-泰勒不稳定性和闪烁噪声。预测的$\max(T_{\rm coh})$通常短于当今运行的音频波段干涉仪的年度观测运行时间，这强调了半相干搜索算法的实用性，该算法将数据划分为多个持续时间为$\max(T_{\rm coh})$的相干段。
英文摘要
Torque balance between gravitational radiation reaction and magnetocentrifugal accretion is one reason why accreting neutron stars rotate slower than centrifugal break-up. Random processes in the accretion disk, such as Rayleigh-Taylor instabilities and flicker noise, drive the spin frequency $f_\ast$ and gravitational wave frequency $f_{\rm gw}\propto f_\ast$ to wander stochastically around their torque balance values. Here it is shown theoretically, in terms of an idealized Ornstein-Uhlenbeck model, that the standard deviation of $f_{\rm gw}$ is given by $σ_{f_{\rm gw}}(h_0) \propto f_{\rm gw} h_0 D βT^{1/2}$, or equivalently $σ_{f_{\rm gw}}(F_{\rm X}) \propto f_{\rm gw}^{1/2} F_{\rm X}^{1/2} D βT^{1/2}$, where $h_0$ is the characteristic wave strain, $F_{\rm X}$ is the X-ray flux, $D$ is the source distance, and $β$ and $T$ are the fractional amplitude and autocorrelation time-scale of the stochastic torque. One can use $σ_{f_{\rm gw}}(h_0)$ and $σ_{f_{\rm gw}}(F_{\rm X})$ to check the physical consistency of a detection candidate in a gravitational wave search by comparing with $σ_{f_{\rm gw}}$ observed. Spin wandering impacts search design, because it sets the maximum time interval $\max(T_{\rm coh})$, during which the signal may be treated as coherent. The Ornstein-Uhlenbeck calculation predicts $10^{-1} \lesssim \max(T_{\rm coh}) / (1\, {\rm day}) \lesssim 10^3$, with $3\times 10^{-2} \lesssim βT^{1/2} / (1 \, {\rm s^{1/2}} ) \lesssim 4$, for Rayleigh-Taylor instabilities and flicker noise. The predicted $\max(T_{\rm coh})$ is shorter typically than the year-long observation runs of audio-band interferometers operating today, emphasizing the utility of semi-coherent search algorithms, which divide the data into multiple coherent segments of duration $\max(T_{\rm coh})$.
发表机构
- University of Melbourne（墨尔本大学）
- Australian Research Council Centre of Excellence for Gravitational Wave Discovery (OzGrav)（澳大利亚研究理事会引力波发现卓越中心（OzGrav））
机构由 AI 辅助整理，请以论文原文为准。
