AI 中文总结
该研究针对LIGO O4a的562个ASAF辐射计候选体，用带隐马尔可夫模型的F统计量匹配滤波器搜索连续引力波，未发现可信信号，且评估了不同类型中子星的探测灵敏度。
AI 中文摘要
我们报告一项针对连续引力波（CWs）的后续搜索，该搜索以LIGO-Virgo-KAGRA（LVK）第四轮观测运行（O4a）全天天球全频率（ASAF）定向辐射计分析的亚阈值候选体为目标。我们使用LVK第四轮观测运行第一部分的Advanced LIGO数据，共分析562个ASAF候选体，每个候选体包含一个窄的1/32 Hz频率带和一个约13平方度的天区像素，以此定义我们分析的搜索参数空间。我们的搜索管道利用配备隐马尔可夫模型的F统计量匹配滤波器，以实现对可能存在的频率漂移CW信号的追踪。在562个初始候选体中，我们获得21个虚警概率小于5%且通过所有仪器否决的异常值；在第四轮观测运行的第二部分中，未在可比统计显著性水平上恢复任何异常值，因此我们得出结论：未检测到可信的CW信号。我们通过恢复添加到真实探测器数据中的模拟信号来评估分析的灵敏度：在20–1726 Hz频率带内，对于孤立中子星（NSs），我们的搜索对应变振幅h₀~(0.63–6.3)×10⁻²⁵达到95%的探测效率；对于长周期（>1年）双星系统中的NSs，应变振幅h₀~(0.82–7.1)×10⁻²⁵时达到95%的探测效率。灵敏度的大范围变化源于探测器噪声的强频率依赖性，尤其在低频段表现显著。
英文摘要
We report on a follow-up search for continuous gravitational waves (CWs) targeting sub-threshold candidates from the O4a LIGO-Virgo-KAGRA (LVK) all-sky all-frequency (ASAF) directed radiometer analysis. We analyze a total of $562$ ASAF candidates using Advanced LIGO data from the first part of the fourth LVK observing run. Each candidate comprises a narrow $1/32$ Hz frequency band paired with a ${\sim}13$ deg$^2$ sky pixel, defining the search parameter space for our analysis. Our search pipeline leverages the $F$-statistic matched filter equipped with a hidden Markov model to enable tracking of a potentially frequency-wandering CW signal. Of the 562 initial candidates, we obtain $21$ outliers with false alarm probability less than $5\%$ that survive all instrumental vetoes. None of the outliers are recovered at comparable statistical significance in the second part of the fourth observing run, from which we conclude that no convincing CW signals are detected. We estimate the sensitivity of our analysis by recovering simulated signals added to real detector data. Across the $20\text{--}1726$ Hz frequency band, our search achieves $95\%$ detection efficiency for strain amplitudes in the range of $h_0\sim (0.63\text{--}6.3)\times10^{-25}$ with respect to isolated neutron stars (NSs), and $h_0\sim (0.82\text{--}7.1)\times10^{-25}$ with respect to NSs in long-period ($>1$ yr) binary systems. The large range in sensitivity is due to the strong frequency dependence of detector noise, particularly at low frequencies.
Comments17 pages, 10 figures
