Precessional dynamics of black hole triples: binary mergers with nearzero effective spin
Abstract
The binary black hole mergers detected by Advanced LIGO/Virgo have shown no evidence of large black hole spins. However, because LIGO/Virgo best measures the effective combination of the two spins along the orbital angular momentum (χ_{eff}), it is difficult to distinguish between binaries with slowly spinning black holes and binaries with spins lying in the orbital plane. Here, we study the spin dynamics for binaries with a distant black hole companion. For spins initially aligned with the orbital angular momentum of the binary, we find that χ_{eff} `freezes' near zero as the orbit decays through the emission of gravitational waves. Through a population study, we show that this process predominantly leads to merging black hole binaries with nearzero χ_{eff}. We conclude that if the detected black hole binaries were formed in triples, then this would explain their low χ_{eff} without the need to invoke nearzero spins or initially large spinorbit angles.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 October 2018
 DOI:
 10.1093/mnrasl/sly126
 arXiv:
 arXiv:1711.07142
 Bibcode:
 2018MNRAS.480L..58A
 Keywords:

 black hole physics;
 gravitational waves;
 stars: kinematics and dynamics;
 Astrophysics  High Energy Astrophysical Phenomena
 EPrint:
 6 pages, 4 figure. Letter accepted for publication in MNRAS