Recoil geometry determines electromagnetic counterparts from supermassive black hole merger remnants

TL;DR

This study uses general relativistic magnetohydrodynamic simulations to explore how recoil geometry affects electromagnetic counterparts from supermassive black hole mergers, revealing diverse jet and disk behaviors.

Contribution

First comprehensive GRMHD simulations of recoiling supermassive black holes interacting with magnetically arrested disks, tracking evolution through inspiral and post-merger phases.

Findings

Recoil direction influences jet formation and disk stability.

Perpendicular recoils sustain relativistic jets, while in-plane recoils cause shock heating and jet quenching.

Oblique recoils induce intermittent jet-disk outbursts.

Abstract

Merging binary black holes embedded in gaseous environments, such as supermassive black hole binaries following gas-rich galaxy mergers, are promising sources of multi-messenger transients in the upcoming age of space-based gravitational wave detections. In case a gravitational radiation recoil is imparted to the merger remnant, subsequent interactions between the recoiled black hole and its circumbinary disk may lead to unique post-merger electromagnetic counterparts. We present the first general relativistic magnetohydrodynamic simulations of a recoiling black hole interacting with a magnetically arrested circumbinary disk the evolution of which has been consistently tracked through the inspiral phase. We show that the post-merger accretion dynamics, depending on the recoil geometry, exhibits qualitatively disparate jet and disk behavior. For recoils perpendicular to the disk, the inner disk remains gravitationally bound and sustains relativistic jets, while in-plane recoils lead to copious shock heating and potential jet quenching for black holes directly colliding with the disk. Oblique recoils, on the other hand, produce intermittent outbursts from jet-disk interactions owing to the tilt introduced in the accretion disk. Multi-wavelength monitoring of these electromagnetic counterparts, in conjunction with the coincident gravitational wave detection, will be able to aid in characterizing the physical conditions of the merger environment.