Finite, intense accretion bursts from tidal disruption of stars on bound orbits

Kimitake Hayasaki*, Nicholas Stone, Abraham Loeb

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

143 Scopus citations

Abstract

We study accretion processes for tidally disrupted stars approaching supermassive black holes on bound orbits, by performing three-dimensional smoothed particle hydrodynamics simulations with a pseudo-Newtonian potential. We find that there is a critical value of the orbital eccentricity below which all the stellar debris remains bound to the black hole. For high but subcritical eccentricities, all the stellar mass is accreted on to the black hole in a finite time, causing a significant deviation from the canonical t-5/3 mass fallback rate. When a star is on a moderately eccentric orbit and its pericentre distance is deeply inside the tidal disruption radius, there can be several orbit crossings of the debris streams due to relativistic precession. This dissipates orbital energy in shocks, allowing for rapid circularization of the debris streams and formation of an accretion disc. The resultant accretion rate greatly exceeds the Eddington rate and differs strongly from the canonical rate of t-5/3. By contrast, there is little dissipation due to orbital crossings for the equivalent simulation with a purely Newtonian potential. This shows that general relativistic precession is crucial for accretion disc formation via circularization of stellar debris from stars on moderately eccentric orbits.

Original languageAmerican English
Pages (from-to)909-924
Number of pages16
JournalMonthly Notices of the Royal Astronomical Society
Volume434
Issue number2
DOIs
StatePublished - Sep 2013
Externally publishedYes

Keywords

  • Accretion
  • Accretion discs
  • Black hole physics
  • Gravitational waves
  • Hydrodynamics

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