AI 中文总结
研究黑洞 X 射线暂现源 A0620-00 的超轨道变化，通过对其长期光学监测分析，识别出超轨道周期，发现信号非随机产生，且系统静止状态与超轨道相位有关，热内吸积流逆行节点进动或可解释观测结果。
AI 中文摘要
静止黑洞低质量 X 射线双星是低光度吸积物理研究的关键对象。A0620-00 作为此类原型系统，数十年来处于 X 射线静止状态，光学变化复杂，其吸积流长期行为尚不清楚。本文报告了对 A0620-00 的长期光学监测分析，数据集跨越近二十年，以 ZTF 光变曲线为周期分析的主要约 2760 天基线。识别出周期为 P = 261.9 ± 9.4 天、峰峰值幅度约 0.2 星等的超轨道周期，信号在三项观测中均可独立恢复，且不太可能仅由随机变化产生。系统的被动和主动静止状态的相对出现似乎取决于超轨道相位，被动状态集中在周期最小值附近，主动状态在最大值附近更常见。在可能的解释中，热内吸积流的逆行节点进动或许能解释观测到的长期调制。在此解释下，周期性信号可能源于内流的周期性重新定向，调制了最内层区域的光度贡献。推断的调制周期对应特征动力学半径约 0.13a（约 10^4 R_g），与外薄盘和内热吸积流之间的预期过渡大致一致。
英文摘要
Quiescent black hole low-mass X-ray binaries provide a key setting for probing accretion physics at low luminosities. A0620-00, the archetypal system in this class, has remained in X-ray quiescence for decades and exhibits complex optical variability, yet the long-term behaviour of its accretion flow remains poorly understood. Here, we report an analysis of long-term optical monitoring of A0620-00 from ZTF, LCO, and ATLAS. The full dataset spans nearly two decades, with the ZTF light curve providing the primary $\sim 2760$-day baseline for the period analysis. We identify a superorbital cycle with a period of $P = 261.9 \pm 9.4$ d and a peak-to-peak amplitude of $\sim 0.2$ mag. The signal is recovered independently across all three surveys, and red-noise simulations indicate that it is unlikely to arise from stochastic variability alone. Furthermore, the relative occurrence of the \textit{passive} and \textit{active} quiescent states displayed by the system seems to depend on the superorbital phase, with passive states concentrated near the cycle minimum and active states more common near maximum. We find that, among the possible interpretations, retrograde nodal precession of a hot inner accretion flow might be able to explain the observed long-term modulation. In this interpretation, the periodic signal may arise from cyclic reorientation of the inner flow, which modulates the photometric contribution from the innermost regions. The inferred modulation period would correspond to a characteristic dynamical radius of $\sim0.13a$ ($\sim10^4~R_{\rm g}$), where $a$ is the binary semi-major axis, broadly consistent with the expected transition between the outer thin disc and the inner hot accretion flow.
CommentsAccepted for publication in A&A
