UCLA

Binaries play an important role in the overall dynamic and evolution of nuclear star clusters. In this dissertation, I explore, using semi-analytic methods, the dynamical evolution of binaries in galactic nuclei after the end of their luminous lives --- starting from supernovae and continuing to the compact object phase --- and their interactions with other cluster objects, in particular the supermassive black hole (SMBH). This stage of evolution can result in many observable phenomena, the abundance and properties of which are highly dependent on the properties of the underlying stellar binary population. Thus, an understanding of the dynamics of stellar remnants is crucial to understanding of the underlying stellar population.

I have shown that natal kicks in stellar binaries during supernovae can trigger a very wide variety of observable phenomena. These include but are not limited to: X-ray binaries, extreme mass ratio inspirals (EMRIs), and hypervelocity objects (including hypervelocity X-ray binaries). The population of X-ray binaries created by supernova kicks is a diagnostic for the black hole (BH) natal kick distribution, which remains highly debated. In particular, we found that no X-ray binaries with a BH primary is created if we assume no BH natal kicks. Subsequent to the natal kicks, most single and binary compact objects (COs) created remain bound to the SMBH. These COs can form gravitational wave (GW) mergers detectable the by Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo, the Laser Interferometer Space Antenna (LISA), and other future GW observatories.

In galactic nuclei, gravitational perturbations by the SMBH can induce eccentricity oscillations in binary COs, resulting in an elevated GW merger rate. I have shown that these eccentricity oscillations can be detected with LISA, out to a few Mpcs. This will allow us distinguish a variety of binary GW sources in galactic nuclei, from sources in other astrophysical environments. As for the single COs, although by themselves they do not emit GWs, in a dense stellar environment like nuclear clusters, they undergo frequent close encounters and emit energy in the form of GWs. If enough energy is emitted, they will form very close very eccentric binaries and merge. I have studied this mechanism as a formation channel for NSBH mergers and found that it is not likely to a major contributor to the overall NSBH rate detectable by LIGO. However, since the rate of merger from this mechanism is highly contingent on the characteristics of the single CO population, especially the density profile, we can use the future observations of NSBH mergers to confirm or revise our current understanding of the nuclear cluster environment.