AI 中文总结
研究了极端可变外观活动星系核IC 3599的第三次巨型X射线爆发，通过“雨燕”等多波段监测，发现其爆发光谱超软、光变曲线有振荡模式等，排除特定爆发情景，为研究极端条件下吸积物理提供关键数据。
AI 中文摘要
我们报告了对特殊的可变外观活动星系核（AGN）IC 3599的一次巨型（因子>100）X射线爆发的发现及多波段后续观测。这是继1990年和2010年两次偶然发现后的第三次此类爆发。基于用“雨燕”对IC 3599的长期监测，第三次爆发发生时即被探测到，并首次在数天至数周内触发多次后续观测。“雨燕”爆发光谱超软，2.5keV以上几乎无光子被探测到。“XMM-牛顿”短期光变曲线显示出明显的类似准周期振荡（QPOs）的振荡模式。光学高态光谱揭示出众多明亮的日冕发射线，这些发射线在低态光谱中不存在或很微弱，而在高态光谱中显著变亮。新结果排除了需要恒定重复时间间隔的爆发情景，但与吸积盘辐射压力不稳定性高度吻合，假设该长期存在的AGN盘中的局部条件影响每次新不稳定性的起始时间。十年时间尺度上反复出现的巨型超软爆发、特殊的发射线响应以及数小时时间尺度上快速的候选准周期短期变化，使IC 3599在AGN中独一无二，确立其为研究极端条件下和爱丁顿极限处吸积物理的关键系统。
英文摘要
We report the discovery and multiwavelength follow-up observations of a giant (factor >100) X-ray outburst of the exceptional changing-look active galactic nucleus (AGN) IC 3599. This is the third such outburst after two previous ones serendipitously discovered in 1990 and 2010. Based on our dedicated long-term monitoring of IC 3599 with {\it Swift}, the third outburst was detected while it was happening, and we triggered multiple follow-up observations within days to weeks for the first time. The Swift outburst spectra are supersoft and almost no photons are detected beyond 2.5 keV. The XMM-Newton short-term light curve shows a remarkable apparent oscillatory pattern that is reminiscent of quasiperiodic oscillations (QPOs). The optical high-state spectra reveal a multitude of bright coronal emission lines that have dramatically brightened and were absent or much fainter in low-state spectra. The new results eliminate outburst scenarios that require a constant time interval of repetitions (like certain variants of repeat tidal stripping, or of an orbiting supermassive black hole impacting the inner accretion disk), but remain in excellent agreement with an accretion disk radiation-pressure instability when assuming that local conditions in the disk of this long-lived AGN affect the onset time of each new instability. The combination of recurrent, giant, supersoft outbursts on decadal timescales, the exceptional emission-line response, and the rapid, candidate quasiperiodic, short-term variability on an hours timescale makes IC 3599 unique among AGN, and establishes it as a key system for studying accretion physics under extreme conditions and at the Eddington limit.
CommentsAccepted for publication in the Astrophysical Journal Letter, 7 figures, 1 Table
