AI 中文总结
研究NGC 6814的X射线光变曲线，利用计时和光谱分析技术，发现食前约45-50微赫兹的周期，食期间周期被调制，通过相位分辨光谱研究其物理原因，可解释为覆盖分数变化或非标准内吸积流，与之前报告一致。
AI 中文摘要
2016年XMM-牛顿卫星对赛弗特1.5星系NGC 6814的X射线光变曲线显示，在一半的观测期间有明显的食现象，有清晰的进蚀和出蚀。本文报告食前光变曲线中的周期性行为。利用计时和光谱分析技术量化该行为并检查周期性信号特征。X射线光变曲线的超小波变换显示，在观测的最初60千秒内有一个约45-50微赫兹的周期，在宽波段（0.3-10千电子伏）和软波段（0.3-1.0千电子伏）的探测显著性均>90%。通过拟合正弦曲线确认了该周期，在最高能段因信噪比降低显著性减弱但仍明显。食期间可变性行为有明显变化，所有能量下测量周期被调制（拉伸）。通过相位分辨光谱研究了这种周期性行为的可能物理原因，发现可解释为覆盖分数的变化或非标准内吸积流（如截断盘和错位流）。非标准内流与之前NGC6814中截断内盘和致密日冕的报告一致。
英文摘要
A 2016 XMM-Newton X-ray light curve of the Seyfert 1.5 galaxy NGC 6814 exhibited clear eclipsing behaviour, with distinct ingress and egress, during half of the observation. Here, we report on the periodic behaviour in the light curve prior to the eclipse. We use timing and spectral analysis techniques to quantify the behaviour and examine the characteristics of the periodic signal. A superlet transform of the X-ray light curve reveals a period of ~45-50 $μ$Hz in the initial 60 ks of the observation with a detection significance at the >90% level in both the broad (0.3-10 keV) and soft (0.3-1.0 keV) bands. The period is confirmed by fitting a sinusoid, and is also evident in the highest energy bands with diminished significance because of reduced signal-to-noise. There appear to be distinct changes in the variability behaviour during the eclipse as the measured period is modulated (stretched) at all energies. From phase-resolved spectra, we investigate possible physical causes of this periodic behaviour and find that it can be interpreted as changes in the covering fraction or a non-standard inner accretion flow (e.g. truncated disc and misaligned flow). The non-standard inner flow appears consistent with previous reports of a truncated inner disc and compact corona in NGC 6814.
Comments17 pages, 15 figures, 2 tables. Accepted for publication in ApJ
