Gravitational interactions of stars with supermassive black hole binaries - i. tidal disruption events

Siva Darbha, Eric R. Coughlin, Daniel Kasen, Eliot Quataert

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


Stars approaching supermassive black holes (SMBHs) in the centres of galaxies can be torn apart by strong tidal forces.We study the physics of tidal disruption by a circular, binary SMBH as a function of the binary mass ratio q = M2/M1 and separation a, exploring a large set of points in the parameter range q [0.01, 1] and a/rt1 [10, 1000]. We simulate encounters in which field stars approach the binary from the loss cone on parabolic, low angular momentum orbits. We present the rate of disruption and the orbital properties of the disrupted stars, and examine the fallback dynamics of the post-disruption debris in the 'frozen-in' approximation. We conclude by calculating the time-dependent disruption rate over the lifetime of the binary. Throughout, we use a primary mass M1 = 106 M as our central example. We find that the tidal disruption rate is a factor of ∼2-7 times larger than the rate for an isolated BH, and is independent of q for q 0.2. In the 'frozen-in' model, disruptions from close, nearly equal mass binaries can produce intense tidal fallbacks: For binaries with q 0.2 and a/rt1 ∼ 100, roughly ∼18-40 per cent of disruptions will have short rise times (trise ∼ 1-10 d) and highly super-Eddington peak return rates (Mpeak/MEdd ∼ 2 × 102-3 × 103).

Original languageEnglish (US)
Pages (from-to)4009-4034
Number of pages26
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
StatePublished - 2018
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Black hole physics
  • Galaxies: nuclei
  • Stars: Kinematics and dynamics
  • Stars: Statistics


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