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

Abstract

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 pericenter passage. We calculate the range of penetration factors $\beta$ vs 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 $\beta \sim 50-127$ for $M/M_{\odot }=10^4$, down to $\beta \sim 5.6-5.9$ for $M/M_{\odot }=10^6$. 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 $t\sim 2$ s with $L\sim 10^{47}$ ergs/s at $E\sim 2$ keV, and the debris has a prompt accretion episode lasting $t\sim$ several min. The events are rare and occur with a rate $\dot{N}\lesssim 10^{-7}$ Mpc${}^{-3}$ yr${}^{-1}$. Ultra-deep TDEs can probe the strong gravity and demographics of low-mass SMBHs.

12 pages, 5 figures

References in corpus (16)

• Advanced LIGO
• The Zwicky Transient Facility: System Overview, Performance, and First Results
• Laser Interferometer Space Antenna
• SPLASH: An interactive visualisation tool for Smoothed Particle Hydrodynamics simulations
• Gravitational-wave sensitivity curves
• Stellar disruption by a supermassive black hole: is the light curve really proportional to $t^{-5/3}$?
• General Relativistic Hydrodynamic Simulation of Accretion Flow from a Stellar Tidal Disruption
• On the mass and luminosity functions of tidal disruption flares: rate suppression due to black hole event horizons
• Tidal disruption events from supermassive black hole binaries
• Tidal disruption events: the role of stellar spin
• Shock waves in tidally compressed stars by massive black holes
• Two fast X-ray transients in archival Chandra data
• Thawing the frozen-in approximation: implications for self-gravity in deeply plunging tidal disruption events
• Tidal disruption of a star in the Schwarzschild spacetime: relativistic effects in the return rate of debris
• Ultra-Close Encounters of Stars With Massive Black Holes: Tidal Disruption Events With Prompt Hyperaccretion
• Gravitational waves from the collision of tidally disrupted stars with massive black holes