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arXiv 1903.03120astro-ph.HE
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AT 2018 dyb的光谱演化和潮汐破裂事件中金属线的存在

The spectral evolution of AT 2018dyb and the presence of metal lines in tidal disruption events

Giorgos Leloudas, Lixin Dai, Iair Arcavi, Paul M. Vreeswijk, Brenna Mockler, Rupak Roy, Daniele B. Malesani, Steve Schulze, Thomas Wevers, Morgan Fraser, Enrico… 展开作者

Giorgos Leloudas, Lixin Dai, Iair Arcavi, Paul M. Vreeswijk, Brenna Mockler, Rupak Roy, Daniele B. Malesani, Steve Schulze, Thomas Wevers, Morgan Fraser, Enrico Ramirez-Ruiz, Katie Auchettl, Jamison Burke, Giacomo Cannizzaro, Panos Charalampopoulos, Ting-Wan Chen, Aleksandar Cikota, Massimo Della Valle, Lluis Galbany, Mariusz Gromadzki, Kasper E. Heintz, Daichi Hiramatsu, Peter G. Jonker, Zuzanna Kostrzewa-Rutkowska, Kate Maguire, Ilya Mandel, Francesca Onori, Matt Nicholl, Nathaniel Roth, Stephen J. Smartt, Lukasz Wyrzykowski, Dave R. Young

摘要:

我们提供了潮汐中断事件(TDE)ASASSN-18 pg/ AT 2018 dyb的光变曲线和光谱,时间跨度为一年。该事件显示了过多的强发射线,包括Balmer系列,He II,He I和O III $λ$ 3760和N III $λλ$ 4100,4640(与He II混合)的金属线。后一种谱线与源自Bowen荧光机制一致。通过分析过去事件的文献谱,我们得出结论,这些线是常见的TDE。因此,光学TDE的光谱多样性比以前认为的要大,并且除了富含H和He的事件之外还包括富含N的事件。我们研究谱线如何随时间演化,通过它们的宽度,相对强度和速度偏移。线的速度宽度开始于$\sim$ 13000 km s $^{-1}$,并随时间减小。He II与N III的比率随时间而增加。ASASSN-14 li也是如此,它的光谱与AT 2018 dyb非常相似,但它的谱线窄了$>$ 2倍。利用$M$- $σ$关系,我们估计了黑洞质量为$M_{\rm BH}$ = $3.3^{+5.0}_{-2.0}\times 10^6$ $M_{\odot}$.这与使用MOSFiT瞬态拟合代码得出的黑洞质量一致。在光谱中探测到强鲍文线是极紫外和(再处理)X射线辐射的间接证据,并有利于TDE光学光度的吸积起源。一个模型,其中光子通过一个超爱丁顿厚盘和它的光学厚风,在一个接近磁盘平面的角度看多次散射后逃逸,是与观测一致的。

英文摘要:

We present light curves and spectra of the tidal disruption event (TDE) ASASSN-18pg / AT 2018dyb spanning a period of one year. The event shows a plethora of strong emission lines, including the Balmer series, He II, He I and metal lines of O III $λ$3760 and N III $λλ$ 4100, 4640 (blended with He II). The latter lines are consistent with originating from the Bowen fluorescence mechanism. By analyzing literature spectra of past events, we conclude that these lines are common in TDEs. The spectral diversity of optical TDEs is thus larger than previously thought and includes N-rich events besides H- and He-rich events. We study how the spectral lines evolve with time, by means of their width, relative strength, and velocity offsets. The velocity width of the lines starts at $\sim$ 13000 km s$^{-1}$ and decreases with time. The ratio of He II to N III increases with time. The same is true for ASASSN-14li, which has a very similar spectrum to AT 2018dyb but its lines are narrower by a factor of $>$2. We estimate a black hole mass of $M_{\rm BH}$ = $3.3^{+5.0}_{-2.0}\times 10^6$ $M_{\odot}$ by using the $M$-$σ$ relation. This is consistent with the black hole mass derived using the MOSFiT transient fitting code. The detection of strong Bowen lines in the optical spectrum is an indirect proof for extreme ultraviolet and (reprocessed) X-ray radiation and favors an accretion origin for the TDE optical luminosity. A model where photons escape after multiple scatterings through a super-Eddington thick disk and its optically thick wind, viewed at an angle close to the disk plane, is consistent with the observations.

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