Understanding formation and properties of gravitational waves events from galactic nuclei

LIGO-Virgo-Kagra观测到的第一个引力波事件为宇宙打开了一个新的可观测窗口。然而，引力波事件的起源仍然是未知的。我们研究了引力波形成事件的几种形成途径，这些途径涉及到少体相互作用和双星演化过程。在Trani et al. 2022 a中，我们研究了在星星团中形成的等级三星如何从黑洞双星、黑洞-中子星和黑洞-白色矮双星中产生引力波事件。我们计算了合并属性和比率，并将其与LIGO-Virgo-Kagra的当前估计进行了比较。在Trani et al. 2022 b中，我们提出了一种新的方法来模拟双星中的共同包络演化，这是双星演化中产生引力波事件所必需的关键阶段。本财政年度完成的进一步研究涉及三重系统的稳定性，这可能影响合并致密双星的形成。最后，我们实现了一种新的方法来模拟星系核中紧凑物体的三体相互作用。我们目前正在进行一项研究：（1）在星系核中三体相遇的结果属性，以更好地了解它们与孤立相遇的区别。这使我们能够分析黑洞合并的偏心率，这可能使我们能够区分其他合并。(2)Kozai-Lidov振荡和星系核中致密双星相遇之间的相互作用。

The first gravitational wave event observed by LIGO-Virgo-Kagra has opened a new observable window on the universe. However, the origin of gravitational wave events is still unknown. We investigated several formation pathways for gravitational wave formation events, which involve few-body interactions and binary stellar evolution processes. In Trani et al. 2022a, we studied how hierarchical triple stars formed in star cluster can produce gravitational wave events from black hole binaries, black hole - neutron stars and black hole - white dwarf binaries. We calculated merger properties and rates, and compared it with the current estimates from LIGO-Virgo-Kagra. In Trani et al. 2022b, we instead proposed a novel way to model the common envelope evolution in binary stars, which is a crucial phase in binary stellar evolution that is necessary to produce gravitational wave events. Further study accomplished in this fiscal year related to the stability of triple systems, which can affect the formation of merging compact binaries. Finally, we have implemented a novel way to model three-body interactions of compact objects in galactic nuclei. We are currently performing a study on: (1) the outcome properties of three-body encounters in galactic nuclei, to better understand how they differ with respect to isolated encounters. This enabled us to analyze the eccentricity of black hole mergers, which may enable us to distinguish from other mergers. (2) The interplay between Kozai-Lidov oscillations and encounters on compact binaries in galactic nuclei.