TAPIR Seminar

In person: 370 Cahill. To Join via Zoom: 868 5298 8404

ABSTRACT: Following the merger of two supermassive black holes (SMBHs), a gravitational wave recoil kick is imparted on the merger remnant due to the anisotropic emission of gravitational waves. These recoil kicks can be as high as ~10^3 km/s which exceeds the escape velocity of most galaxies, and these super-kicks can lead to ejected or rogue SMBHs. While there are several candidates, recoiling SMBHs are difficult to uniquely identify since observations so far cannot rule out alternate possibilities such as dual active galactic nuclei. Here, we present a novel observational signature: off-nuclear or extragalactic tidal disruption events of stars by recoiling SMBHs. When a super-kick is imparted on a SMBH, there is a tightly bound cluster of stars recoiling with it. We show that these bound stars should be in an eccentric, apse-aligned disk where stars are strongly torqued to extremely high eccentricities. The corresponding rate of tidal disruption events in an eccentric disk is expected to be of order ~0.1 yr^-1 gal^-1, several orders of magnitude higher than in an isotropic cluster. We show that this high expected rate of tidal disruption events in an eccentric disk implies off-nuclear or extragalactic tidal disruption events as viable and likely observables of a recoiling or rogue SMBH.