Astrophysical Gravitational-Wave Echoes from Galactic Nuclei

Understand

Galactic nuclei (GNs) are dense stellar environments abundant in gravitational-wave (GW) sources for LIGO, VIRGO, and KAGRA.

• The GWs may be generated by stellar-mass black hole (BH) or neutron star mergers following gravitational bremsstrahlung, dynamical scattering encounters, Kozai-Lidov type oscillations driven by the central supermassive black hole (SMBH), or gas-assisted mergers if present.
• In this paper, we examine a smoking gun signature to identify sources in GNs: the GWs scattered by the central SMBH.
• This produces a secondary signal, an astrophysical GW echo, which has a very similar time-frequency evolution as the primary signal but arrives after a time delay.