发表机构
National Central University（中央大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文利用35年X射线数据，提出秩搜索法识别Her X-1的新反常低态，并揭示其超轨道相位演化的平滑与变化交替模式及盘质量变化机制。
AI 中文摘要
利用长达35年的多仪器X射线观测基线，系统研究了X射线双星Her X-1的35天超轨道调制。我们开发了一种基于主高态峰值强度的秩搜索方法，以客观且可复现的标准识别反常低态（ALS）。该方法重现了已知的反常低态，识别出两个此前未被认识到的候选事件——ALS 1991和ALS 2015，并独立重现了最近报道的ALS 2025。随后，我们刻画了长期超轨道相位演化，识别出七个在平滑行为与变化行为之间交替的时期。平滑成分由三次趋势经验描述，而周期性变化时期的特征时标约为3400天。在一阶倾斜盘框架内，长期相位演化对应于推断的累积盘质量增加约1.8%和外盘半径扩张约0.9%，而短期相位偏移可由盘质量变化（≲2.4%）重现。约168天的黏性扩散时标为短期盘响应提供了特征时标。最后，主高态与短高态之间稳定的相位关系和高度轮廓相似性表明，翘曲盘在观测基线上保持了极其稳定的全局几何结构。
英文摘要
The 35-day superorbital modulation of the X-ray binary Her X-1 was systematically investigated using a 35-year multi-instrument X-ray observational baseline. We developed a Rank-Searching method using the peak intensity of the main high state to identify anomalous low states (ALSs) with an objective and reproducible criterion. The method recovers the known ALSs, identifies two previously unrecognized candidate episodes, ALS 1991 and ALS 2015, and independently recovers the recently reported ALS 2025. We then characterized the long-term superorbital phase evolution, identifying seven epochs that alternate between smooth and variable behavior. The smooth component is empirically described by a cubic trend, while the recurrent variable epochs have a characteristic timescale of approximately 3400 days. Within a first-order tilted-disk framework, the secular phase evolution corresponds to an inferred cumulative disk-mass increase of $\sim1.8\%$ and an outer-disk-radius expansion of $\sim0.9\%$, while the short-term phase excursions can be reproduced by disk-mass variations of $\lesssim2.4\%$. A viscous diffusion timescale of approximately 168 days provides a characteristic timescale for the short-term disk response. Finally, the stable phase relation and high profile similarity between the main and short high states indicate that the warped disk maintains a remarkably stable global geometry over the observational baseline.
Comments21 pages, 9 figures, submitted to The Astrophysical Journal
