The Bardeen-Petterson effect in accreting supermassive black-hole binaries: a systematic approach. (arXiv:2004.02894v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Gerosa_D/0/1/0/all/0/1">Davide Gerosa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rosotti_G/0/1/0/all/0/1">Giovanni Rosotti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Barbieri_R/0/1/0/all/0/1">Riccardo Barbieri</a>

Disc-driven migration is a key evolutionary stage of supermassive black-hole
binaries hosted in gas-rich galaxies. Besides promoting the inspiral, viscous
interactions tend to align the spin of the black hole with the orbital angular
momentum of the disc. We present a critical and systematic investigation of
this problem, also known as the Bardeen-Petterson effect. We design a new
iterative scheme to solve the non-linear dynamics of warped accretion discs
under the influence of both relativistic frame-dragging and binary companion.
We characterize the impact of the disc “critical obliquity”, which marks
regions of the parameter space where viable evolutionary paths cease to exist.
We find that black-hole spins reach either complete alignment or a critical
configuration. Our findings are important to predict the spin configurations
with which supermassive black-hole binaries enter their gravitational-wave
driven regime and become detectable by LISA.

Disc-driven migration is a key evolutionary stage of supermassive black-hole
binaries hosted in gas-rich galaxies. Besides promoting the inspiral, viscous
interactions tend to align the spin of the black hole with the orbital angular
momentum of the disc. We present a critical and systematic investigation of
this problem, also known as the Bardeen-Petterson effect. We design a new
iterative scheme to solve the non-linear dynamics of warped accretion discs
under the influence of both relativistic frame-dragging and binary companion.
We characterize the impact of the disc “critical obliquity”, which marks
regions of the parameter space where viable evolutionary paths cease to exist.
We find that black-hole spins reach either complete alignment or a critical
configuration. Our findings are important to predict the spin configurations
with which supermassive black-hole binaries enter their gravitational-wave
driven regime and become detectable by LISA.

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