Stability Analysis of Circular Geodesics in Dyonic Dilatonic Black Hole Spacetimes

TL;DR

This paper analyzes the stability of circular geodesics around a specific class of dyonic dilatonic black holes, revealing how the innermost stable circular orbit depends on the model's parameters through polynomial solutions.

Contribution

It provides a detailed stability analysis of circular geodesics in dyonic dilatonic black hole spacetimes, including the derivation of ISCO conditions for all parameter values.

Findings

ISCO determined by solving a fourth-order polynomial

Stability characteristics depend on the dilatonic coupling parameter

Results applicable to understanding quasinormal modes in these spacetimes

Abstract

This research investigates a non-extreme dyonic-like dilatonic charged black hole solution within a four-dimensional gravity model. This model incorporates two scalar (dilaton) fields and two Abelian vector fields, with interactions between the scalar and vector fields mediated by exponential terms involving two dilatonic coupling vectors. The solution is characterized by a dimensionless parameter $a$ (where $0 < a < 2$), which is specifically defined as a function of the dilatonic coupling vectors. The paper further explores solutions for timelike and null circular geodesics, which are crucial for understanding various astrophysical scenarios, including the quasinormal modes of different test fields in the eikonal approximation. For all values of $a$ the innermost stable circular orbit (ISCO) are found by means of reducing the problem to the solution of fourth order polynomial equation.