Distinguishing Black-Hole Spin-Orbit Resonances by their Gravitational-Wave Signatures




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American Physical Society



If binary black holes form following the successive core collapses of sufficiently massive binary stars, precessional dynamics may align their spins, S₁ and S₂, and the orbital angular momentum L into a plane in which they jointly precess about the total angular momentum J. These spin orientations are known as spin-orbit resonances since S₁, S₂, and L all precess at the same frequency to maintain their planar configuration. Two families of such spin-orbit resonances exist, differentiated by whether the components of the two spins in the orbital plane are either aligned or antialigned. The fraction of binary black holes in each family is determined by the stellar evolution of their progenitors, so if gravitational-wave detectors could measure this fraction they could provide important insights into astrophysical formation scenarios for binary black holes. In this paper, we show that even under the conservative assumption that binary black holes are observed along the direction of J (where precession-induced modulations to the gravitational waveforms are minimized), the waveforms of many members of each resonant family can be distinguished from all members of the other family in events with signal-to-noise ratios ρ ≃10, typical of those expected for the first detections with Advanced LIGO and Virgo. We hope that our preliminary findings inspire a greater appreciation of the capability of gravitational-wave detectors to constrain stellar astrophysics and stimulate further studies of the distinguishability of spin-orbit resonant families in more expanded regions of binary black-hole parameter space.



Angular momentum, Spin orbit resonances, Double stars, Black holes (Astronomy)


"We thank M. Pürrer and the referee for helpful feedback. D. G. is supported by the United Kingdom Science and Technology Facility Council and the Isaac Newton Studentship of the University of Cambridge. E. B. is supported by the NSF CAREER Grant No. PHY-1055103. R. O. S. is supported by the NSF Grants No. PHY-0970074 and No. PHY-1307429. U.S. is supported by the FP7-PEOPLE-2011-CIG Grant No. 293412 “CBHEO,” the FP7-PEOPLE-2011-IRSES Grant No. 295189 “NRHEP,” the STFC GR Roller Grant No. ST/L000636/1, the Cosmos system, part of DiRAC, funded by STFC and BIS under Grants No. ST/K00333X/1 and No. ST/J005673/1, the NSF XSEDE Grant No. PHY-090003, and CESGA-ICTS Grant No. 249. Figures have been generated using the Python-based matplotlib package."


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