Friday, October 30, 2026 at 12:15 pm

JILA Foothills Room

Mark Dodici , University of Toronton

"Dynamics of stellar binaries orbiting massive black holes"

Abstract:

Binary stars near massive black holes (MBHs) produce a wide range of observable phenomena—like hypervelocity stars, repeating tidal disruption events, X-ray binaries, and mergers of stars and compact objects—but the properties of these binaries are scarcely understood. I'll talk about two novel theoretical results on this topic. First, in a galactic nucleus (a dense star cluster dominated by the potential of an MBH, found at the centers of most galaxies), roughly 2 in 5 stellar binaries should shrink to near-contact separations through three-body dynamics and efficient tidal friction. This shrinking boosts predicted hypervelocity star speeds and X-ray binary formation rates. Second, when a galactic nucleus is "active," hosting a massive gas disk, that disk can cause a large number of binaries to be separated by the tidal gravity of the MBH. These separations eject one member of the binary from the nucleus at great speed and place the other on an orbit very close to the MBH. These two results may help solve two observational puzzles surrounding transient events in the centers of other galaxies.

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