Datensatz

Zusammenfassung

Precession in black-hole binaries is caused by a misalignment between the
total spin and the orbital angular momentum. The gravitational-wave emission of
such systems is anisotropic, which leads to an asymmetry in the $\pm m$
multipoles when decomposed into a spherical harmonic basis. This asymmetric
emission can impart a kick to the merger remnant black hole as a consequence of
linear momentum conservation. Despite the astrophysical importance of kicks,
multipole asymmetries contribute very little to the overall signal strength
and, therefore, the majority of current gravitational-wave models do not
include them. Recent efforts have been made to include asymmetries in waveform
models. However, those efforts focus on capturing finer features of precessing
waveforms without making explicit considerations of remnant kick velocities.
Here we close that gap and present a comprehensive analysis of the linear
momentum flux expressed in terms of multipole asymmetries. As expected, large
asymmetries are needed to achieve the largest kick velocities. Interestingly,
the same large asymmetries may lead to negligible kick velocities if the
antisymmetric and symmetric waveform parts are perpendicular to each other
around merger. We also present a phenomenological tool for testing the
performance of waveform models with multipole asymmetries. This tool helped us
to fix an inconsistency in the phase definition of the IMRPhenomXO4a waveform
model.