揭示变状态活动星系核中的吸积盘结构：NGC1566

中文摘要 AI 辅助

NGC1566是一个低质量（约6×10^6 M☉）的活动星系核（AGN），其吸积流具有异常大幅度的变异性。在光学波段，它在重复出现的短暂亮态（具有强烈的蓝/紫外连续谱和清晰的宽发射线）与较弱的持续态（没有强宽发射线）之间循环，使其成为一个重复变状态（CS）AGN。我们重新分析了2018年亮耀斑期间密集的光学/紫外和X射线监测数据，首次展示了（扣除宿主星系后的）光学/紫外AGN光谱以及X射线发射的相应演化。如同在其他CS-AGN中所见，最强的光谱演化发生在紫外/软X射线成分中，该成分在低于0.01L_Edd时可能消失，而热冕和更红的光学/紫外成分显示出较弱的变异性。我们表明，红色光学发射可能是来自外盘的内在发射与再处理发射，以及来自宽线区（BLR）的漫射连续谱的复合体，并讨论了这在变状态事件中为连续谱反响映射所预示的不同特征。历史光变曲线显示，重复的变状态事件与光变曲线中异常大幅度的离散耀斑相关联。虽然这些事件似乎不是周期性的，但该行为支持了先前的建议，即吸积流被反复扰动，可能是由一个中等质量黑洞伴星引起的。

英文摘要

NGC1566 is a low mass ($\sim 6\times 10^6M_\odot$) Active Galactic Nuclei (AGN) with unusual large amplitude variabilty in its accretion flow. In the optical it cycles between recurring short bright episodes with strong blue/UV continuum and clear broad line emission, and a much weaker persistent level without strong broad lines, making it a repeating changing-state (CS) AGN. We re-analyse the intensive optical/UV and X-ray monitoring during the 2018 bright flare, showing for the first time the corresponding evolution of the (host galaxy subtracted) optical/UV AGN spectrum as well as the X-ray emission. As seen in other CS-AGN, the strongest spectral evolution is in a UV/soft X-ray component which likely disappears below $0.01L_{\rm Edd}$ while the hot corona and a redder optical/UV component show weaker variability. We show that the red optical emission is likely a composite of the intrinsic and reprocessed emission from the outer disc, together with diffuse continuum from the BLR, and discuss the different signatures predicted by this for continuum reverberation across the changing-state event. The historical lightcurves show repeated changing-state events tied to unusually large amplitude discrete flares in the lightcurve. While these do not appear to be periodic, the behaviour does support previous suggestions that the accretion flow is repeatedly perturbed, perhaps by an intermediate mass black hole companion.

发表机构

• Peking University（北京大学）
• University of Durham（杜伦大学）
• INAF Osservatorio Astronomico di Roma（意大利国家天体物理研究所罗马天文台）

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