Catching the Flare - Tracing Short-term AGN Outbursts via Daily Robotic Spectroscopy

人们普遍认为，活动星系核（AGN）是由物质有效地吸积到其中心的超大质量黑洞上提供动力的。由此产生的中心电离辐射在不同的时间尺度上是可变的，可能是由于物质的不连续流入。 根据活动星系核的标准范例，在SMBH附近有两个结构，每个结构的范围从光日到光月：（1）吸积盘，产生可变的紫外线和光学连续辐射;（2）宽线区（BLR），中心和可变的电离辐射产生同样可变的，但时间延迟的宽发射线。 高度变化的活动星系核在只有几天到几个月的极小时间尺度上表现出非常强烈的通量变化，变化幅度超过30%，甚至高达几百%。 所谓“变貌活动星系核”是指活动星系核在宽发射谱线上还表现出强烈的光谱变化。 然而，目前的AD和BLR模型无法解释的短期爆发和变化，这是不一致的标准模型的Shakura-Sunyaev吸积盘，观察到的高度可变和变化的AGN。 显然，目前的AD和BLR模型需要更新或扩展其结构和运动学，以考虑短期的连续谱带和谱线的变化。 在这里，我们建议使用哥廷根的机器人MONET/南望远镜，在我们唯一的处置，配备了一个积分场摄谱仪，以执行一个每天的节奏光谱和光度监测活动的样本1016非常高的变化，和变化的AGN。与此同时，我们将在ASAS-SN巡天的帮助下，每周从修订的Shapley-Ames目录中观察400个明亮的南半球星系，以寻找额外的高度可变和变化的AGN。将通过相关技术分析获得的连续谱和线发射光变曲线，并获得有关AD结构和BLR运动学的高质量信息。这个项目将能够回答这样一个问题，即高度可变和变化的活动星系核是否表现出不同的结构和不同的运动学，例如，与“正常”活动星系核相比，活动星系核的流入/流出行为随时间变化，并为考虑短期变化的更新模型奠定基础。

It is generally accepted that active galactic nuclei (AGN) are powered by the efficient accretion of matter onto supermassive black holes at their center. The resulting central ionizing radiation is variable on different time-scales, probably due to a discontinuous inflow of matter. According to the standard AGN paradigm, there are two structures, each with an extent of light-days to light-months, in the direct vicinity of the SMBH: (1) The accretion disk, which generates variable UV and optical continuum emission, and (2) the broad-line region (BLR), where the central and variable ionizing radiation generates likewise variable, but time-delayed broad-emission lines. Highly-variable AGN show extraordinarily strong variations in flux by more than 30 up to several 100 percent on extremely small time-scales of only days to months. “Changing-look AGN” are defined as AGN additionally exhibiting strong spectral changes of the broad-emission lines. However, current models of the AD and the BLR are not able to explain the short-term outbursts and variations, which are inconsistent with the standard model of a Shakura-Sunyaev accretion disc, observed in highly-variable and changing-look AGN. Evidently, current AD and BLR models need to be updated or extended with regard to their structure and kinematics to account for short-term variations in the continuum bands and line profiles. Here we propose to use Göttingen’s robotic MONET/South telescope, at our sole disposal, equipped with an integral field spectrograph to perform a daily-cadence spectroscopic and photometric monitoring campaign of a sample of ∼16 extraordinarily high-variable, and changing-look AGN. In parallel, we will – with the help of the ASAS-SN survey – watch 400 bright southern galaxies from the Revised Shapley-Ames Catalog on a weekly basis in order to look for additional highly-variable and changing-look AGN. The obtained continuum and line emission light-curves will be analysed by means of correlation techniques and result in high-quality information about the AD structure and the kinematics of the BLR. This project will be able to answer the question whether highly-variable and changing-look AGN exhibit a different structure and different kinematics, e.g., a time-dependent change of the inflow/outflow behaviour, than “normal” AGN, and lay the ground for updated models that take short-term variations into account.