A Luminous X-Ray Transient in SDSS J143359.16+400636.0: A Likely Tidal Disruption Event
A Luminous X-Ray Transient in SDSS J143359.16+400636.0: A Likely Tidal Disruption Event
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DOI：
10.3847/1538-4357/abde34
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发表时间：
2020-10
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通讯作者：
M. Brightman;C. Ward;D. Stern;K. Mooley;K. De;S. Gezari;S. van Velzen;I. Andreoni;M. Graham-M.-Grah
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作者：
M. Brightman;C. Ward;D. Stern;K. Mooley;K. De;S. Gezari;S. van Velzen;I. Andreoni;M. Graham-M.-Grah
我们介绍了斯威夫特 X 射线望远镜于 2020 年 2 月 5 日偶然发现的发光 X 射线瞬变现象，该现象位于 SDSS J143359.16+400636.0 星系的核心，z = 0.099（光度距离 D L = 456 Mpc）。观察到瞬态在 0.3-10 keV X 射线波段达到~1044 erg s−1 的峰值光度，这比峰值光学/紫外光度高~20 倍。来自 Zwicky 瞬态设施和 Swift 的光学、紫外和 X 射线光曲线显示，来自光源的通量下降与 t −5/3 一致，并且 NuSTAR 和 Chandra 的观测显示软 X 射线光谱，光子指数 Г = 2.9 ± 0.1。 X射线/紫外线特性与众所周知的活跃星系核特性不一致，并且与已知的X射线潮汐破坏事件（TDE）有更多共同点，使我们得出结论，这很可能是一次TDE。宽带光谱能量分布可以通过盘内温度为 K 的盘黑体模型很好地描述，盘发射的大部分 (>40%) 向上散射到 X 射线波段。 X射线探测后用Keck/LRIS拍摄的光谱显示了宿主星系中的LINER线比率，表明在事件发生之前超大质量黑洞上有低水平的吸积，但没有看到宽线或TDE的其他迹象。恒星速度色散意味着为该事件提供动力的超大质量黑洞的质量为 log(M BH/M ⊙) = 7.41 ± 0.41，我们估计该事件的爱丁顿分数在峰值时约为 50%。这种可能的 TDE 并未通过广域光学勘测或光谱学来识别，这表明如果没有广域紫外线或 X 射线勘测，将会错过更多类似的事件。
We present the discovery of a luminous X-ray transient, serendipitously detected by Swift’s X-ray Telescope on 2020 February 5, located in the nucleus of the galaxy SDSS J143359.16+400636.0 at z = 0.099 (luminosity distance D L = 456 Mpc). The transient was observed to reach a peak luminosity of ∼1044 erg s−1 in the 0.3–10 keV X-ray band, which was ∼20 times more than the peak optical/UV luminosity. Optical, UV, and X-ray light curves from the Zwicky Transient Facility and Swift show a decline in flux from the source consistent with t −5/3, and observations with NuSTAR and Chandra show a soft X-ray spectrum with photon index Γ = 2.9 ± 0.1. The X-ray/UV properties are inconsistent with well-known active galactic nucleus properties and have more in common with known X-ray tidal disruption events (TDEs), leading us to conclude that it was likely a TDE. The broadband spectral energy distribution can be described well by a disk blackbody model with an inner disk temperature of K, with a large fraction (>40%) of the disk emission upscattered into the X-ray band. An optical spectrum taken with Keck/LRIS after the X-ray detection reveals LINER line ratios in the host galaxy, suggesting low-level accretion onto the supermassive black hole prior to the event, but no broad lines or other indications of a TDE were seen. The stellar velocity dispersion implies that the mass of the supermassive black hole powering the event is log(M BH/M ⊙) = 7.41 ± 0.41, and we estimate that at peak the Eddington fraction of this event was ∼50%. This likely TDE was not identified by wide-field optical surveys or optical spectroscopy, indicating that more events like this would be missed without wide-field UV or X-ray surveys.