# The secular tidal disruption of stars by low-mass Super Massive Black Holes secondaries in galactic nuclei

**Authors:** Giacomo Fragione, Nathan Leigh  
**arXiv:** [1803.10107](https://arxiv.org/abs/1803.10107)  
**Date:** 2018-03-27  
**Summary page:** https://www.summarizepaper.com/en/paper/1803.10107v1/

## Key points

- Tidal disruption events (TDEs) are useful for detecting single super massive black holes (SMBHs) in galactic nuclei
- TDEs occur when stars get too close to an SMBH and are torn apart, producing a strong electromagnetic flare
- High-precision direct N-body simulations were used to investigate how stars orbiting an intermediate-mass black hole (IMBH) secondary are perturbed by an SMBH primary
- Stellar orbits are severely affected by the primary SMBH due to secular effects, resulting in depleted regions of parameter space corresponding to large stellar orbital inclinations with respect to the SMBH-IMBH orbital plane
- Above a critical SMBH mass of approximately 1.15 x 10^8 solar masses, no TDE event can occur for typical stars in an old stellar population since the Schwarzschild radius exceeds the tidal disruption radius, meaning any TDEs due to such massive SMBHs will remain dark
- The rate of TDE occurrence can be as high as approximately 10^-2 - 10^-1 per year and most TDEs occur on a timescale of approximately 0.5 million years
- Stars may be ejected with velocities up to thousands of kilometers per second, which could contribute to the observed population of Galactic hypervelocity stars

## Summary

The study of tidal disruption events (TDEs) provides a useful probe of the presence of single super massive black holes (SMBHs) in galactic nuclei. TDEs occur when stars pass too close to an SMBH and are torn apart by its gravitational forces, producing a strong electromagnetic flare. While a few TDE candidates have been observed, the majority remain dark. In this paper, Giacomo Fragione and Nathan Leigh use high-precision direct N-body simulations to investigate how stars orbiting an intermediate-mass black hole (IMBH) secondary are perturbed by an SMBH primary. They find that the evolution of stellar orbits is severely affected by the primary SMBH due to secular effects, resulting in depleted regions of parameter space corresponding to large stellar orbital inclinations with respect to the SMBH-IMBH orbital plane. Stars orbiting with high inclinations end their lives as TDEs due to Kozai-Lidov oscillations, illuminating the secondary SMBH/IMBH. The researchers show that above a critical SMBH mass of approximately 1.15 x 10^8 solar masses, no TDE event can occur for typical stars in an old stellar population since the Schwarzschild radius exceeds the tidal disruption radius. Consequently, any TDEs due to such massive SMBHs will remain dark. This means that no TDEs should be observed in galaxies more massive than approximately 4.15 x 10^10 solar masses unless a lower-mass secondary SMBH or IMBH is also present. The secular mechanism for producing TDEs considered here therefore offers a useful probe of SMBH-SMBH/IMBH binarity in the most massive galaxies. The researchers further show that the rate of TDE occurrence can be as high as approximately 10^-2 - 10^-1 per year and that most TDEs occur on a timescale of approximately 0.5 million years. Additionally, stars may be ejected with velocities up to thousands of kilometers per second, which could contribute to the observed population of Galactic hypervelocity stars.