Massive black hole binaries (MBHBs) with masses of ∼104 to ∼1010, M⊙ are one of the main targets for currently operating and forthcoming space-borne gravitational wave observatories. In this paper, we explore the effect of the stellar host rotation on the bound binary hardening efficiency, driven by three-body stellar interactions. As seen in previous studies, we find that the centre of mass (CoM) of a prograde MBHB embedded in a rotating environment starts moving on a nearly circular orbit about the centre of the system shortly after the MBHB binding. In our runs, the oscillation radius is ≈ 0.25 (≈ 0.1) times the binary influence radius for equal mass MBHBs (MBHBs with mass ratio 1:4). Conversely, retrograde binaries remain anchored about the centre of the host. The binary shrinking rate is twice as fast when the binary CoM exhibits a net orbital motion, owing to a more efficient loss cone repopulation even in our spherical stellar systems. We develop a model that captures the CoM oscillations of prograde binaries; we argue that the CoM angular momentum gain per time unit scales with the internal binary angular momentum, so that most of the displacement is induced by stellar interactions occurring around the time of MBHB binding, while the subsequent angular momentum enhancement gets eventually quashed by the effect of dynamical friction. The effect of the background rotation on the MBHB evolution may be relevant for LISA sources, that are expected to form in significantly rotating stellar systems.

Varisco, L., Bortolas, E., Dotti, M., Sesana, A. (2021). Stellar hardening of massive black hole binaries: The impact of the host rotation. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 508(1), 1533-1542 [10.1093/mnras/stab2649].

Stellar hardening of massive black hole binaries: The impact of the host rotation

Varisco L.
;
Bortolas E.;Dotti M.;Sesana A.
2021

Abstract

Massive black hole binaries (MBHBs) with masses of ∼104 to ∼1010, M⊙ are one of the main targets for currently operating and forthcoming space-borne gravitational wave observatories. In this paper, we explore the effect of the stellar host rotation on the bound binary hardening efficiency, driven by three-body stellar interactions. As seen in previous studies, we find that the centre of mass (CoM) of a prograde MBHB embedded in a rotating environment starts moving on a nearly circular orbit about the centre of the system shortly after the MBHB binding. In our runs, the oscillation radius is ≈ 0.25 (≈ 0.1) times the binary influence radius for equal mass MBHBs (MBHBs with mass ratio 1:4). Conversely, retrograde binaries remain anchored about the centre of the host. The binary shrinking rate is twice as fast when the binary CoM exhibits a net orbital motion, owing to a more efficient loss cone repopulation even in our spherical stellar systems. We develop a model that captures the CoM oscillations of prograde binaries; we argue that the CoM angular momentum gain per time unit scales with the internal binary angular momentum, so that most of the displacement is induced by stellar interactions occurring around the time of MBHB binding, while the subsequent angular momentum enhancement gets eventually quashed by the effect of dynamical friction. The effect of the background rotation on the MBHB evolution may be relevant for LISA sources, that are expected to form in significantly rotating stellar systems.
Articolo in rivista - Articolo scientifico
black hole physics; Galaxy: kinematics and dynamics; gravitational waves; methods: numerical; stars: kinematics and dynamics;
English
2021
508
1
1533
1542
partially_open
Varisco, L., Bortolas, E., Dotti, M., Sesana, A. (2021). Stellar hardening of massive black hole binaries: The impact of the host rotation. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 508(1), 1533-1542 [10.1093/mnras/stab2649].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/458178
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