Electromagnetic counterparts from counter-rotating relativistic kicked discs

TL;DR

This study uses relativistic hydrodynamical simulations to compare the behavior and electromagnetic luminosity of co-rotating and counter-rotating discs around merging supermassive black holes, revealing significant differences in luminosity and timing.

Contribution

It provides the first detailed comparison of co-rotating and counter-rotating discs in post-merger black hole systems using relativistic simulations, highlighting their distinct luminosity behaviors.

Findings

Counter-rotating discs can be 2-12 times more luminous than co-rotating ones.

Luminosity peaks occur approximately 10 days later in counter-rotating discs.

Black hole spin affects the luminosity differently for co-rotating and counter-rotating discs.

Abstract

We show the results of two dimensional general relativistic inviscid and isothermal hydrodynamical simulations comparing the behavior of co-rotating (with respect to the black hole rotation) and counter-rotating circumbinary quasi-Keplerian discs in the post merger phase of a supermassive binary black hole system. While confirming the spiral shock generation within the disc due to the combined effects of mass loss and recoil velocity of the black hole, we find that the maximum luminosity of counter-rotating discs is a factor ~(2-12) higher than in the co-rotating case, depending on the spin of the black hole. On the other hand, the luminosity peak happens ~10 days later with respect to the co-rotating case, for a binary with a total mass M~10^6 M_\odot. Although the global dynamics of counter-rotating discs in the post merger phase of a merging event is very similar to that for co-rotating discs, an important difference has been found. In fact, increasing the spin of the central black hole produces more luminous co-rotating discs while less luminous counter-rotating ones.