Current gravitational-wave data from stellar-mass black-hole binary mergers suggest a correlation between the binary mass ratio q and the effective spin χeff: more unequal-mass binaries consistently show larger and positive values of the effective spin. Multiple generations of black-hole mergers in dense astrophysical environments may provide a way to form unequal-mass systems, but they cannot explain the observed correlation on their own. We show that the symmetry of the astrophysical environment is a crucial feature to shed light on this otherwise puzzling piece of observational evidence. We present a toy model that reproduces, at least qualitatively, the observed correlation. The model relies on axisymmetric, disklike environments where binaries participating in hierarchical mergers share a preferential direction. Migration traps in AGN disks are a prime candidate for this setup, hinting at the exciting possibility of constraining their occurrence with gravitational-wave data.
Santini, A., Gerosa, D., Cotesta, R., Berti, E. (2023). Black-hole mergers in disklike environments could explain the observed q−χeff correlation. PHYSICAL REVIEW D, 108(8) [10.1103/PhysRevD.108.083033].
Black-hole mergers in disklike environments could explain the observed q−χeff correlation
Davide Gerosa;
2023
Abstract
Current gravitational-wave data from stellar-mass black-hole binary mergers suggest a correlation between the binary mass ratio q and the effective spin χeff: more unequal-mass binaries consistently show larger and positive values of the effective spin. Multiple generations of black-hole mergers in dense astrophysical environments may provide a way to form unequal-mass systems, but they cannot explain the observed correlation on their own. We show that the symmetry of the astrophysical environment is a crucial feature to shed light on this otherwise puzzling piece of observational evidence. We present a toy model that reproduces, at least qualitatively, the observed correlation. The model relies on axisymmetric, disklike environments where binaries participating in hierarchical mergers share a preferential direction. Migration traps in AGN disks are a prime candidate for this setup, hinting at the exciting possibility of constraining their occurrence with gravitational-wave data.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.