Binary disruptions driven by massive disks around massive black holes
arXiv:2607.26205
The paper investigates how the non‑spherical gravitational potential of massive accretion disks around massive black holes can torque binary stars, driving them to extreme eccentricities that cause binary disruptions via the Hills mechanism, producing hypervelocity and S‑cluster stars.
Abstract
Accretion disks around massive black holes (MBHs) in galactic nuclei can contain significant mass, in which case their non-spherical potentials exert significant torques on single and binary stars orbiting the MBHs. These torques can drive orbits to very large eccentricities. Previous works have shown that this driving can cause disruptions of single stars by the tidal gravity of the MBH. Here, we characterize the ability of these torques to drive binary stars to the point of disruption via the Hills mechanism. We derive semi-analytical estimates, validated with numerical simulations, of the number of binary disruptions driven by a generic disk in a generic nucleus. Using these results, we estimate that the formation of the ~5-Myr-old disk of stars in the Galactic Center drove a burst of ~10^2 binary disruptions. These disruptions produced an excess of S-cluster stars and hypervelocity stars --- possibly including S5-HVS1, the fastest-known hypervelocity star. In other galaxies, analogues of S-cluster stars produced by this process may evolve into tidal disruption events following a disk phase. Hypervelocity star observations may help clarify the importance of disk-driven disruptions, which eject stars nearly isotropically and in temporal bursts --- a unique combination among processes driving binary disruptions.
16 pages, 11 figures (main text) + 8 pages, 2 figures (appendices). To be submitted to AAS Journals. Comments welcome!