Tidal Disruption Flares from Recoiling Supermassive Black Holes

TL;DR

This paper explores observable electromagnetic signatures, especially X-ray flares, from stars tidally disrupted by recoiling supermassive black holes ejected from galaxy centers.

Contribution

It provides calculations of disruption rates and predicts unique off-nuclear and intergalactic flare signatures for recoiling black holes.

Findings

Disruption rates are comparable to non-recoiling black holes.

Recoiling black holes produce powerful off-nuclear X-ray flares.

Additional signatures include episodic X-ray emission and intergalactic supernovae.

Abstract

Supermassive black holes ejected from galaxy nuclei by gravitational wave recoil will carry a retinue of bound stars, even in the absence of an accretion disk. We discuss the observable signatures related to these stars, with an emphasis on electromagnetic flares from stars that are tidally disrupted by the black hole. We calculate disruption rates for the bound, and the unbound, stars. The rates are smaller than, but comparable to, rates for non-recoiling black holes. A key observational consequence is the existence of powerful off-nuclear and intergalactic X-ray flares. We also discuss other observable signatures associated with the bound stars, including episodic X-ray emission from accretion due to stellar mass loss; intergalactic supernovae; and feedback trails.