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arXiv 2008.06512astro-ph.SRastro-ph.GA
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社会上遥远的邻居：使用双星来限制银河系中心物体的密度

On Socially Distant Neighbors: Using Binaries to Constrain the Density of Objects in the Galactic Center

Sanaea C. Rose, Smadar Naoz, Abhimat K. Gautam, Andrea M. Ghez, Tuan Do, Devin Chu, Eric Becklin

备注：
Accepted to ApJ, 20 pages, 11 figures
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摘要：

恒星通常以双星的形式存在。银河系中心（GC）中围绕超大质量黑洞（SMBH）的核星团预计将包括一个双星群体。在这个稠密的环境中，双星经常会遇到邻近的恒星并与之相互作用。这些相互作用从微小的扰动到剧烈的碰撞不等。在前一种情况下，弱引力相互作用解除了软双星在蒸发时间尺度上的束缚，这取决于双星的性质以及周围物体的密度和速度色散。类似地，碰撞也可以解开一个二进制，碰撞率取决于密度。因此，具有已知属性的二进制的检测可以约束GC中的密度分布，这意味着紧凑对象的数量，否则检测起来很有挑战性。我们估计的密度在其生命周期内的任意偏心率的SMBH的轨道解开一个二进制。我们发现偏心率对密度约束的影响很小。在此概念证明中，我们以假设的年轻和旧二进制文件为例，证明该过程可以探测GC中的密度。类似地，已知的密度分布提供了对双星轨道分离的约束。我们的研究结果强调需要考虑多个动力学过程串联。在某些情况下，往往更接近SMBH，碰撞时标，而不是蒸发时标给出了更严格的密度约束，而其他二进制远离SMBH提供不可靠的密度约束，因为它们向内迁移，由于质量偏析。

英文摘要：

Stars often reside in binary configurations. The nuclear star cluster surrounding the supermassive black hole (SMBH) in the Galactic Center (GC) is expected to include a binary population. In this dense environment, a binary frequently encounters and interacts with neighboring stars. These interactions vary from small perturbations to violent collisions. In the former case, weak gravitational interactions unbind a soft binary over the evaporation timescale, which depends on the binary properties as well as the density of surrounding objects and velocity dispersion. Similarly, collisions can also unbind a binary, and the collision rate depends on the density. Thus, the detection of a binary with known properties can constrain the density profile in the GC with implications for the number of compact objects, which are otherwise challenging to detect. We estimate the density necessary to unbind a binary within its lifetime for an orbit of arbitrary eccentricity about the SMBH. We find that the eccentricity has a minimal impact on the density constraint. In this proof of concept, we demonstrate that this procedure can probe the density in the GC using hypothetical young and old binaries as examples. Similarly, a known density profile provides constraints on the binary orbital separation. Our results highlight the need to consider multiple dynamical processes in tandem. In certain cases, often closer to the SMBH, the collision timescale rather than the evaporation timescale gives the more stringent density constraint, while other binaries farther from the SMBH provide unreliable density constraints because they migrate inwards due to mass segregation.

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