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Line-force driven wind from a thin disk in tidal disruption event

De-Fu Bu, Xiao-Hong Yang, Liang Chen, Chenwei Yang, Guobin Mou

TL;DR

This study demonstrates that even a compact sub-Eddington thin disk in a tidal disruption event can launch a substantial line-force driven wind. Using 2D hydrodynamic simulations, the authors show wind launching and acceleration predominantly inside $r<30R_s$ with speeds up to $0.3c$, and mass and kinetic energy carried at the level of a few percent of the Eddington values. The wind strength peaks around an Eddington ratio of $\varepsilon\approx0.6$ due to ionization effects on the line-force multiplier. The results have observational implications for radio emission from wind–CNM or wind–cloud interactions, offering a potential diagnostic for the environment around quiescent supermassive black holes in TDEs.

Abstract

Winds from the accretion disk in tidal disruption events (TDEs) play a key role in determining the radiation of TDEs. The winds from the super-Eddington accretion phase in TDEs have recently been studied. However, properties of the winds from the sub-Eddington accretion disk in TDEs are not clear. We aim to investigate properties of winds from the circularized sub-Eddington accretion disk in TDEs. We study the line force driven accretion disk wind. We perform two-dimensional hydrodynamic simulations using the PLUTO code to study the line force driven wind from the circularized accretion disk around a $10^6$ solar mass black hole in TDEs. We find that although the disk has a very small size in TDEs, strong wind can be driven by line force when the disk have luminosity higher than $20\%$ of the Eddington luminosity. The maximum velocity of wind can be as high as $0.3$ times the speed of light. The kinematic power of wind is in the range of $1\%-6\%$ times the Eddington luminosity. Strong wind can be driven by line force from the thin disk around a $10^6$ solar mass black hole in TDEs. We briefly discuss the possible radio emission from the shock when the wind collides with the surrounding medium.

Line-force driven wind from a thin disk in tidal disruption event

TL;DR

This study demonstrates that even a compact sub-Eddington thin disk in a tidal disruption event can launch a substantial line-force driven wind. Using 2D hydrodynamic simulations, the authors show wind launching and acceleration predominantly inside with speeds up to , and mass and kinetic energy carried at the level of a few percent of the Eddington values. The wind strength peaks around an Eddington ratio of due to ionization effects on the line-force multiplier. The results have observational implications for radio emission from wind–CNM or wind–cloud interactions, offering a potential diagnostic for the environment around quiescent supermassive black holes in TDEs.

Abstract

Winds from the accretion disk in tidal disruption events (TDEs) play a key role in determining the radiation of TDEs. The winds from the super-Eddington accretion phase in TDEs have recently been studied. However, properties of the winds from the sub-Eddington accretion disk in TDEs are not clear. We aim to investigate properties of winds from the circularized sub-Eddington accretion disk in TDEs. We study the line force driven accretion disk wind. We perform two-dimensional hydrodynamic simulations using the PLUTO code to study the line force driven wind from the circularized accretion disk around a solar mass black hole in TDEs. We find that although the disk has a very small size in TDEs, strong wind can be driven by line force when the disk have luminosity higher than of the Eddington luminosity. The maximum velocity of wind can be as high as times the speed of light. The kinematic power of wind is in the range of times the Eddington luminosity. Strong wind can be driven by line force from the thin disk around a solar mass black hole in TDEs. We briefly discuss the possible radio emission from the shock when the wind collides with the surrounding medium.
Paper Structure (16 sections, 34 equations, 11 figures)

This paper contains 16 sections, 34 equations, 11 figures.

Table of Contents

  1. Introduction
  2. Numerical method
  3. Basic equations
  4. Initial and boundary conditions
  5. Result
  6. Overview of structure of line force driven wind
  7. Eddington ratio dependence
  8. Discussion and observational applications
  9. Summary
  10. Line force multiplier
  11. Derivation of the scaling law for the thin disk density in Equation 8
  12. Dependence on physical parameters
  13. The inner radial boundary
  14. The disk outer boundary
  15. The ratio of X-ray luminosity to disk luminosity
  16. ...and 1 more sections

Figures (11)

  • Figure 1: Time-averaged logarithm gas density (color) in ${\rm g \ cm^{-3}}$ and velocity (vectors) for $\varepsilon=0.8$. The $z$-axis is the rotational axis of the accretion disk. The accretion disk surface is at the $z=0$ plane.
  • Figure 2: Time-averaged radial profile of wind mass flux (top-panel), kinetic power (middle panel) and momentum flux (bottom panel) for the model with $\varepsilon = 0.8$.
  • Figure 3: Time-averaged angular profile of wind mass flux (top-panel), radial velocity (bottom panel) measured at the outer radial boundary for the model with $\varepsilon = 0.8$.
  • Figure 4: Mass flux (top-panel) and kinematic power (bottom panel) of wind measured at the outer radial boundary as a function of Eddington ratio.
  • Figure 5: Time-averaged radial profiles of wind mass flux for models with inner radial boundary at $10R_{\rm s}$ (solid line, fiducial model in Section 3.1), $15R_{\rm s}$ (dotted line) and $20R_{\rm s}$ (dashed line) with $\varepsilon = 0.8$.
  • ...and 6 more figures