标题： 黑洞暂现源Swift J1658.2-4242极端翻转状态过渡中的潜在时钟 显示英文标题

标题： An underlying clock in the extreme flip-flop state transitions of the black hole transient Swift J1658.2-4242

摘要： 目标：翻转现象（flip-flops）是一种类似于倒钟形的X射线流量变化，在一些暂现吸积黑洞双星系统中出现，并且伴随着光谱硬度和功率密度谱（PDS）的同时变化。 它们发生在这些系统的演化中的关键阶段，此时吸积盘发射开始主导过冕发射。 翻转现象只有极少数被观测到，并且理解得很少。 方法：我们在2018年Swift J1658.2-4242爆发期间，利用XMM-Newton、NuSTAR、Astrosat、Swift、Insight-HXMT、INTEGRAL和ATCA的观测数据检测到了15次翻转现象。我们分析了它们的光变曲线，搜索了周期性信号，计算了它们的PDS，并拟合了它们的X射线能谱，以研究翻转过渡期间源的行为，以及展示翻转现象间隔与其他爆发阶段的区别。 结果：Swift J1658.2-4242的翻转现象属于极端类型，其流量差异高达77%，持续时间约为100秒，比之前观测到的情况大得多。我们观察到与尖锐流量变化同步的PDS发生显著变化，展示了从未见过的C型和A型准周期振荡之间的转变。PDS的变化滞后于光变曲线，但比光变曲线中的变化更快。翻转现象出现在两个间隔中，这两个间隔之间相隔两周未观察到这些现象。两次翻转状态之间的转换发生在基本周期的随机整数倍上，第一个间隔的基本周期为2.761ks，第二个间隔为2.61ks。光谱分析显示高流量和低流量的翻转状态相似，但不同于没有翻转现象的区间。吸积盘内温度的变化是导致翻转现象中大部分流量差异的原因。我们强调修正尘埃散射晕对X射线能谱影响的重要性。 显示英文摘要

摘要： Aims: Flip-flops are top-hat-like X-ray flux variations which occur in some transient accreting black hole binary systems and feature simultaneous changes in the spectral hardness and the Power Density Spectrum (PDS). They occur at a crucial time in the evolution of these systems, when the accretion disk emission starts to dominate over coronal emission. Flip-flops have only rarely been observed and are poorly understood. Methods: We detect 15 flip-flops in the 2018 outburst of Swift J1658.2-4242, in observations by XMM-Newton, NuSTAR, Astrosat, Swift, Insight-HXMT, INTEGRAL, and ATCA. We analyse their light curves, search for periodicities, compute their PDS, and fit their X-ray spectra, to investigate the source behaviour during flip-flop transitions, and how the interval featuring flip-flops differs from the rest of the outburst. Results: The flip-flops of Swift J1658.2-4242 are of an extreme variety, exhibiting flux differences of up to 77% within ~100s, much larger than has been seen so far. We observe radical changes in the PDS simultaneous with the sharp flux variations, featuring transitions between the Quasi-Periodic Oscillation types C and A, which have never been observed before. Changes to the PDS are delayed, but more rapid than changes in the light curve. Flip-flops occur in two intervals, separated by two weeks in which these phenomena were not seen. Transitions between the two flip-flop states occurred at random integer multiples of a fundamental period, of 2.761ks in the first interval, and 2.61ks in the second. Spectral analysis reveals the high and low flux flip-flop states to be similar, but distinct from intervals lacking flip-flops. A change in the inner temperature of the accretion disk is responsible for most of the flux difference in the flip-flops. We highlight the importance of correcting for the influence of the dust scattering halo on the X-ray spectra.