Uncovering Hidden Massive Black Hole Companions with Tidal Disruption Events

Abstract

Dynamical perturbations from supermassive black hole (SMBH) binaries can increase the rates of tidal disruption events (TDEs). However, most previous work focuses on TDEs from the heavier black hole in the SMBH binary (SMBHB) system. In this work, we focus on the lighter black holes in SMBHB systems and show that they can experience a similarly dramatic increase in their TDE rate due to perturbations from a more massive companion. While the increase in TDEs around the more massive black hole is mostly due to chaotic orbital perturbations, we find that, around the smaller black hole, the eccentric Kozai–Lidov mechanism is dominant and capable of producing a comparably large number of TDEs. In this scenario, the mass derived from the light curve and spectra of TDEs caused by the lighter SMBH companion is expected to be significantly smaller than the SMBH mass estimated from galaxy scaling relations, which are dominated by the more massive companion. This apparent inconsistency can help find SMBHB candidates that are not currently accreting as active galactic nuclei and that are at separations too small for them to be resolved as two distinct sources. In the most extreme cases, these TDEs provide us with the exciting opportunity to study SMBHBs in galaxies where the primary SMBH is too massive to disrupt Sun-like stars.

Keywords

• Black holes
• High energy astrophysics
• Time domain astronomy
• Transient sources
• Supermassive black holes
• Galaxy mergers