Impact of antisymmetric contributions to signal multipoles in the measurement of blackhole spins
Abstract
Many current models for the gravitationalwave signal from precessing blackhole binaries neglect an asymmetry in the $\pm m$ multipoles. The asymmetry is weak, but is responsible for outofplane recoil, which for the final black hole can be several thousand km/s. In this work we show that the multipole asymmetry is also necessary to accurately measure the blackhole spins. We consider synthetic signals calculated from the numerical relativity surrogate model NRSur7dq4, which includes the multipole asymmetry, and measure the signal parameters using two versions of the same model, one with and one without the multipole asymmetry included. We find that in high signaltonoiseratio observations where the spin magnitude and direction can in principle be measured accurately, neglecting the multipole asymmetry can result in biased measurements of these quantities. Measurements of the blackhole masses and the standard alignedspin combination $\chi_{\rm eff}$ are not in general strongly affected. As an illustration of the impact of the multipole asymmetry on a real signal we consider the LVK observation GW200129_065458, and find that the inclusion of the multipole asymmetry is necessary to identify the binary as unequalmass and a high inplane spin in the primary.
 Publication:

arXiv eprints
 Pub Date:
 February 2024
 DOI:
 10.48550/arXiv.2402.00813
 arXiv:
 arXiv:2402.00813
 Bibcode:
 2024arXiv240200813K
 Keywords:

 General Relativity and Quantum Cosmology
 EPrint:
 14 pages, 8 figures