Ultra-deep tidal disruption events: Prompt self-intersections and observables

Siva Darbha, Eric R. Coughlin, Daniel Kasen, Chris Nixon

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


A star approaching a supermassive black hole (SMBH) can be torn apart in a tidal disruption event (TDE). We examine ultra-deep TDEs, a new regime in which the disrupted debris approaches close to the black hole's Schwarzschild radius, and the leading part intersects the trailing part at the first pericentre passage. We calculate the range of penetration factors β versus SMBH masses M that produce these prompt self-intersections using a Newtonian analytic estimate and a general relativistic (GR) geodesic model. We find that significant self-intersection of Solar-type stars requires β ∼ 50-127 for M/M☉ = 104, down to β ∼ 5.6-5.9 for M/M☉ = 106. We run smoothed particle hydrodynamic (SPH) simulations to corroborate our calculations and find close agreement, with a slightly shallower dependence on M. We predict that the shock from the collision emits an X-ray flare lasting t ∼ 2 s with L ∼ 1047 erg s−1 at E ∼ 2 keV, and the debris has a prompt accretion episode lasting t ∼ several minutes. The events are rare and occur with a rate N ≲ 10−7 Mpc−3 yr−1. Ultra-deep TDEs can probe the strong gravity and demographics of low-mass SMBHs.

Original languageEnglish (US)
Pages (from-to)5267-5278
Number of pages12
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - Oct 1 2019
Externally publishedYes


  • Black hole physics
  • Galaxies: nuclei
  • Relativistic processes
  • Stars: kinematics and dynamics
  • X-rays: bursts

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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