论文标题
解读核瞬态ERASST J045650.3-203750的极端X射线变异性：可能重复的部分潮汐破坏事件
Deciphering the extreme X-ray variability of the nuclear transient eRASSt J045650.3-203750: A likely repeating partial tidal disruption event
论文作者
论文摘要
（删节）在本文中，我们介绍了出色的重复X射线核瞬变的结果，即Erasst J045650.3-203750（以下简称J0456-20），该X射线均由SRG/Erosita在Z〜0.077的RedShift iS quiescent Galaxy中发现。主要结果是：1）J0456-20循环穿过四个独特的阶段：X射线上升阶段，通向X射线高原阶段，持续约2个月。这是由快速的X射线通量降低阶段终止的，在此过程中，X射线通量可以在1周内大幅下降超过100倍以上，然后在X射线微弱状态下大约两个月，然后再开始X射线上升阶段。 2）X射线光谱通常在上升阶段柔软，光子指数> 3.0，并且随着X射线通量的增加而变得更难。有证据表明，在X射线上升阶段开始时，具有$ T_ \ text {in} = 70 $ eV的内部区域温度的多色磁盘。高质量的XMM-NEWTON数据表明，在高原阶段和上升阶段的明亮末端，通过软盘种子光子的反构造，温暖而热的电晕可能是X射线发射的原因。 3）J0456-20仅显示适度的紫外线变异性，没有显着的光学变异性； 4）仅在X射线高原阶段（尚未检测到）无线电发射，并显示2周的时间尺度迅速下降。我们得出的结论是，J0456-20可能是重复的核瞬变，暂定复发时间约为223天。我们讨论了解释J0456-20的观察性质的几种可能性，目前赞成重复的部分潮汐破坏事件（TDE）是最有可能的情况。长期的X射线演化被解释为以热磁盘为主的软性状态和陡峭的幂律状态之间的过渡，这意味着可以在几个月内形成电晕并在几周内摧毁。
(Abridged) In this paper, we present the results of an exceptional repeating X-ray nuclear transient, eRASSt J045650.3-203750 (hereafter J0456-20), uncovered by SRG/eROSITA in a quiescent galaxy at redshift of z~0.077. The main results are: 1) J0456-20 cycles through four distinctive phases: an X-ray rising phase leading into an X-ray plateau phase which lasts for ~2 months. This is terminated by a rapid X-ray flux drop phase during which the X-ray flux can drastically drop by more than a factor of 100 within 1 week followed by an X-ray faint state for about two months before it starts the X-ray rising phase again; 2) the X-ray spectra are generally soft in the rising phase with a photon index >3.0, and become harder as the X-ray flux increases. There is evidence of a multi-colour disk with inner region temperature of $T_\text{in}=70$ eV at the beginning of the X-ray rising phase. The high quality XMM-Newton data suggest that a warm and hot corona could be responsible for the X-ray emission, through inverse Comptonisation of soft disk seed photons, during the plateau phase and at the bright end of the rising phase; 3) J0456-20 shows only moderate UV variability and no significant optical variability; 4) radio emission is only detected (as yet) in the X-ray plateau phase, and shows a rapid decline on a time-scale of 2 weeks. We conclude that J0456-20 is likely a repeating nuclear transient with a tentative recurrence time of ~223 days. We discuss several possibilities to explain J0456-20's observational properties, and currently favour a repeating partial tidal disruption event (TDE) as the most likely scenario. The long-term X-ray evolution is explained as a transition between a thermal disk-dominated soft state and a steep power-law state, implying that the corona can be formed within a few months and destroyed within a few weeks.
