用潮汐扰动白矮星的光发射线探测中等质量黑洞
Probing Intermediate Mass Black Holes With Optical Emission Lines from Tidally Disrupted White Dwarfs
摘要：
我们计算了白矮星（WD）被中等质量黑洞（IMBH; $M\sim 10^{2}-10^{5}\msun$）潮汐破坏时释放的碎片产生的发射线光谱，并探讨了使用发射线来识别此类事件并约束IMBH属性的可能性。为此，我们采用和适应的技术开发的Strubbe和Quataert研究的光学发射线时产生的主序星（MS）的潮汐中断的超大质量黑洞。WD在$< 10^{5}\msun$黑洞的事件视界之外被潮汐破坏，这使得这些潮汐破坏事件成为IMBH的良好路标。我们专注于光学和紫外线发射线时产生的吸积耀斑光电离的碎片流，在中断期间仍然未绑定。我们发现光谱主要由C和O离子的谱线所支配，其中最强的谱线是早期的\ion{C}{4} $λ$ 1549和后期的[ \ion{O}{3} ] $λ$ 5007。此外，我们在[ \ion{O}{3} ] $λλ$ 4959，5007双峰的发射线的轮廓建模，并发现它是高度不对称的速度宽度高达$\sim 2500 \rm{\;km\;s^{-1}}$，这取决于WD-IMBH系统的属性和观察者的方向。最后，我们比较了模型与观测的X射线耀斑和光学发射线的核心的球状星团，并提出如何未来的观测可以测试，如果这些功能是由于WD已潮汐中断的IMBH。
英文摘要：
We calculate the emission line spectrum produced by the debris released when a white dwarf (WD) is tidally disrupted by an intermediate-mass black hole (IMBH; $M\sim 10^{2}-10^{5}\msun$) and we explore the possibility of using the emission lines to identify such events and constrain the properties of the IMBH. To this end, we adopt and adapt the techniques developed by Strubbe & Quataert to study the optical emission lines produced when a main sequence (MS) star is tidally disrupted by a supermassive black hole. WDs are tidally disrupted outside of the event horizon of a $< 10^{5}\msun$ black hole, which makes these tidal disruption events good signposts of IMBHs. We focus on the optical and UV emission lines produced when the accretion flare photoionizes the stream of debris that remains unbound during the disruption. We find that the spectrum is dominated by lines due to ions of C and O, the strongest of which are \ion{C}{4} $λ$1549 at early times and [\ion{O}{3}] $λ$5007 at later times. Furthermore, we model the profile of the emission lines in the [\ion{O}{3}] $λλ$4959, 5007 doublet and find that it is highly asymmetric with velocity widths of up to $\sim 2500 \rm{\;km\;s^{-1}}$, depending on the properties of the WD-IMBH system and the orientation of the observer. Finally, we compare the models with observations of X-ray flares and optical emission lines in the cores of globular clusters and propose how future observations can test if these features are due to a WD that has been tidally disrupted by an IMBH.
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