Merger estimates for rotating Kerr black holes in modified gravity

TL;DR

This paper investigates how black hole mergers in modified gravity differ from general relativity, analyzing orbital dynamics, ringdown modes, and final spins, revealing dependence on scalar field parameters.

Contribution

It systematically studies the signatures of black hole mergers in modified gravity, including geodesic orbits, quasinormal modes, and final spins, highlighting the influence of scalar fields.

Findings

Black hole merger signatures depend on scalar field parameters.

Orbital and ringdown characteristics vary with black hole spin and scalar field.

Final spins of merged black holes are estimated using established recipes.

Abstract

In this paper, we explore the signatures of non-rotating and rotating black hole mergers in the matter-free modified gravity. First, we solve the unstable circular null orbits and the innermost stable circular timelike orbits via the geodesic motion. The characteristic quantities of these orbits are systematically analyzed by varying the black hole spin and the scalar field parameter of the gravity. Then based on it, we study the ringdown modes from the light ring/quasinormal modes correspondence. The final spins of the merged black holes are also estimated with the Buonanno-Kidder-Lehner recipe. Several black hole merging cases are investigated in detail. All these results show that the black hole mergers are closely dependent of the scalar field parameter of the gravity.