# Quasinormal modes of Einstein-Gauss-Bonnet-dilaton black holes

## TL;DR

This paper analyzes the quasinormal modes of Einstein-Gauss-Bonnet-dilaton black holes, revealing differences from Schwarzschild black holes and identifying unstable secondary branches that could impact gravitational wave observations.

## Contribution

It provides the first detailed study of axial and polar quasinormal modes for Einstein-Gauss-Bonnet-dilaton black holes across multiple perturbation modes.

## Key findings

- Primary branch modes differ from Schwarzschild modes by up to 10%
- Secondary branch is unstable with long-lived modes
- Potential observable effects on gravitational wave ringdown signals

## Abstract

We study quasinormal modes of static Einstein-Gauss-Bonnet-dilaton black holes. Both axial and polar perturbations are considered and studied from $l=0$ to $l=3$. We emphasize the difference in the spectrum between the Schwarzschild solutions and dilatonic black holes. At large Gauss-Bonnet coupling constant a small secondary branch of black holes is present, when the dilaton coupling is sufficiently strong. The modes of the primary branch can differ from the Schwarzschild modes up to $10\%$. The secondary branch is unstable and possesses long-lived modes. We address the possible effects of these modes on future observations of gravitational waves emitted during the ringdown phase of astrophysical black holes.