Shu Xinwen, Zhang Wenjie, Li Shuo, Jiang Ning, Dou Liming, Yan Zhen, Xie Fu-Guo, Shen Rongfeng, Sun Luming, Liu Fukun, Wang Tinggui
Department of Physics, Anhui Normal University, Wuhu, Anhui, 241002, China.
National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100101, China.
Nat Commun. 2020 Nov 18;11(1):5876. doi: 10.1038/s41467-020-19675-z.
Optical transient surveys have led to the discovery of dozens of stellar tidal disruption events (TDEs) by massive black hole in the centers of galaxies. Despite extensive searches, X-ray follow-up observations have produced no or only weak X-ray detections in most of them. Here we report the discovery of delayed X-ray brightening around 140 days after the optical outburst in the TDE OGLE16aaa, followed by several flux dips during the decay phase. These properties are unusual for standard TDEs and could be explained by the presence of supermassive black hole binary or patchy obscuration. In either scenario, the X-rays can be produced promptly after the disruption but are blocked in the early phase, possibly by a radiation-dominated ejecta which leads to the bulk of optical and ultraviolet emission. Our findings imply that the reprocessing is important in the TDE early evolution, and X-ray observations are promising in revealing supermassive black hole binaries.
光学瞬变巡天已发现了数十起星系中心大质量黑洞引发的恒星潮汐瓦解事件（TDE）。尽管进行了广泛搜索，但在大多数此类事件中，X射线后续观测未检测到X射线或仅检测到微弱的X射线。在此，我们报告在TDE OGLE16aaa的光学爆发后约140天发现了延迟的X射线增亮现象，随后在衰减阶段出现了几次流量下降。这些特性对于标准TDE来说是不寻常的，可能是由超大质量黑洞双星的存在或斑块状遮挡所解释。在任何一种情况下，X射线都可能在瓦解后迅速产生，但在早期阶段被阻挡，可能是被以辐射为主的抛射物阻挡，而这种抛射物会产生大部分的光学和紫外线辐射。我们的发现表明，再处理在TDE的早期演化中很重要，并且X射线观测有望揭示超大质量黑洞双星。
