Study on the detectability of gravitational radiation from single-binary
encounters between black holes in nuclear star cluster: the case of
hyperbolic flybys
Elena Codazzo, Matteo Di Giovanni, Jan Harms, Marco Dall'Amico, Michela Mapelli
With the release of the third Gravitational-Wave Transient Catalogue
(GWTC-3), 90 observations of compact-binary mergers by Virgo and LIGO detectors
are confirmed. Some of these mergers are suspected to have occurred in star
clusters. The density of black holes at the cores of these clusters is so high
that mergers can occur through a few generations forming increasingly massive
black holes. These conditions also make it possible for three black holes to
interact, most likely via single-binary encounters. In this paper, we present a
first study of how often such encounters can happen in nuclear star clusters
(NSCs) as a function of redshift, and whether these encounters are observable
by gravitational-wave (GW) detectors. This study focuses on effectively
hyperbolic encounters leaving out the resonant encounters. We find that in NSCs
single-binary encounters occur rarely compared to binary mergers, and that
hyperbolic encounters most likely produce the strongest GW emission below the
observation band of terrestrial GW detectors. While several of them can be
expected to occur per year with peak energy in the LISA band, their amplitude
is low, and detection by LISA seems improbable.
Preprint
Comment: 14 pages, 9 figures
Subjects: Astrophysics - High Energy Astrophysical Phenomena; Astrophysics - Cosmology and Nongalactic Astrophysics; General Relativity and Quantum Cosmology