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Modeling Tidal Disruption Events and Compact Object Plunges in Nuclear Star Clusters

Philip Cho, Kai Wu, Francesco Flammini Dotti, Taras Panamarev, Rainer Spurzem

TL;DR

The paper investigates SMBH growth channels in nuclear star clusters by analyzing tidal disruption events and compact-object inspirals using high-resolution direct N-body simulations with NBODY6++GPU/STARDISK. It introduces a bound-debris TDE model based on orbital parameters and an EMRI inspiral model via the Peters formula $t_{\rm merge}$, enabling a more integrated treatment of dynamics and relativistic mergers. Key findings show TDEs peak early (approximately $2$ Myr) with about 50% of disrupted mass bound and accreted, and EMRIs predominantly have pericenters in $4r_s$–$27r_s$, while SMBH growth from TDEs remains modest and the inspiral criterion requires refinement. These results support TDEs and EMRIs as SMBH-growth channels in NSCs and lay the groundwork for DRAGON-III simulations with larger $N$ and longer evolution.

Abstract

We study tidal disruption events (TDEs) and compact object inspirals in nuclear star clusters (NSCs) hosting a central supermassive black hole (SMBH), focusing on their role in SMBH growth. Using the STARDISK version of the direct N-body code NBODY6++GPU, we perform pilot simulations with two improved models: one for mass fallback from TDEs and another for compact object plunges based on orbital decay timescales. Our results show that mass accretion via TDEs peaks within the first 2 Myr and decreases more rapidly for higher initial SMBH masses, with roughly half the disrupted stellar debris being accreted. Compact object accretion is confined mostly to orbits with pericenters between 4 and 27 Schwarzschild radii and is suppressed by an order of magnitude when inspiral criteria are applied.

Modeling Tidal Disruption Events and Compact Object Plunges in Nuclear Star Clusters

TL;DR

The paper investigates SMBH growth channels in nuclear star clusters by analyzing tidal disruption events and compact-object inspirals using high-resolution direct N-body simulations with NBODY6++GPU/STARDISK. It introduces a bound-debris TDE model based on orbital parameters and an EMRI inspiral model via the Peters formula , enabling a more integrated treatment of dynamics and relativistic mergers. Key findings show TDEs peak early (approximately Myr) with about 50% of disrupted mass bound and accreted, and EMRIs predominantly have pericenters in –, while SMBH growth from TDEs remains modest and the inspiral criterion requires refinement. These results support TDEs and EMRIs as SMBH-growth channels in NSCs and lay the groundwork for DRAGON-III simulations with larger and longer evolution.

Abstract

We study tidal disruption events (TDEs) and compact object inspirals in nuclear star clusters (NSCs) hosting a central supermassive black hole (SMBH), focusing on their role in SMBH growth. Using the STARDISK version of the direct N-body code NBODY6++GPU, we perform pilot simulations with two improved models: one for mass fallback from TDEs and another for compact object plunges based on orbital decay timescales. Our results show that mass accretion via TDEs peaks within the first 2 Myr and decreases more rapidly for higher initial SMBH masses, with roughly half the disrupted stellar debris being accreted. Compact object accretion is confined mostly to orbits with pericenters between 4 and 27 Schwarzschild radii and is suppressed by an order of magnitude when inspiral criteria are applied.
Paper Structure (5 sections, 3 figures)

This paper contains 5 sections, 3 figures.

Table of Contents

  1. Introduction
  2. Methodology
  3. Initial Conditions
  4. Results
  5. Conclusions and Outlook

Figures (3)

  • Figure 1: TDE distribution by time, color-coded by the bound debris mass fraction. Normalized histograms of distributions are shown on top of the plots.
  • Figure 2: Evolution of SMBH mass growth (left panel) and mass accretion rates (right panel).
  • Figure 3: Pericenter distances of stellar-mass black holes at the time of accretion. Blue dots represent those with eccentric orbits, and orange dots represent those with hyperbolic orbits. The simulation time of 400NB is approximately 4Myr