王者归来：FO Aquarii从2016年前所未有的低状态中恢复的时间序列测光
Return of the King: Time-Series Photometry of FO Aquarii's Initial Recovery from its Unprecedented 2016 Low State
摘要：
2016年5月，在观测历史上首次探测到中极FO~Aqr处于低态。我们报告的时间分辨测光的系统在其初始恢复从这个微弱的状态。我们的数据，其中包括高速测光的节奏只有2秒，显示存在非常强的周期性在22.5分钟和11.26分钟，相当于自旋轨道拍频和两倍的值，分别。自旋频率的脉冲也存在，但幅度比在亮态中通常观察到的要低得多。通过比较我们的功率谱与理论模型，我们推断，大量的吸积是流喂养在我们的观察，在对比的磁盘喂吸积占主导地位的明亮的状态。此外，我们发现，FO~Aqr的恢复速度与其他磁激变变星的恢复速度相比异常缓慢，$e$ -折叠时间为115 $\pm7$天。恢复还显示了在10天的跨度高达0.2等的亮度中值的不规则变化。最后，我们表明，自旋脉冲的到达时间取决于系统的整体亮度。
英文摘要：
In 2016 May, the intermediate polar FO~Aqr was detected in a low state for the first time in its observational history. We report time-resolved photometry of the system during its initial recovery from this faint state. Our data, which includes high-speed photometry with cadences of just 2 sec, shows the existence of very strong periodicities at 22.5 min and 11.26 min, equivalent to the spin-orbit beat frequency and twice its value, respectively. A pulse at the spin frequency is also present but at a much lower amplitude than is normally observed in the bright state. By comparing our power spectra with theoretical models, we infer that a substantial amount of accretion was stream-fed during our observations, in contrast to the disk-fed accretion that dominates the bright state. In addition, we find that FO~Aqr's rate of recovery has been unusually slow in comparison to rates of recovery seen in other magnetic cataclysmic variables, with an $e$-folding time of 115$\pm7$ days. The recovery also shows irregular variations in the median brightness of as much as 0.2~mag over a 10-day span. Finally, we show that the arrival times of the spin pulses are dependent upon the system's overall brightness.
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