Circular geodesics in the field of double-charged dilatonic black holes

TL;DR

This paper investigates circular geodesics around a specific class of non-extreme dilatonic charged black holes with two scalar and vector fields, analyzing their properties and implications for astrophysical phenomena.

Contribution

It provides explicit solutions for timelike and null circular geodesics in a novel four-dimensional dilatonic black hole model, including the radii of innermost stable orbits for specific parameter values.

Findings

Derived solutions for circular geodesics in the black hole spacetime.

Calculated innermost stable circular orbit radii for specific parameter values.

Analyzed implications for quasinormal modes and astrophysical scenarios.

Abstract

A non-extreme dilatonic charged (by two ``color electric'' charges) black hole solution is examined within a four-dimensional gravity model that incorporates two scalar (dilaton) fields and two Abelian vector fields. The scalar and vector fields interact through exponential terms containing two dilatonic coupling vectors. The solution is characterized by a dimensionless parameter $a$ $(0 < a < 2)$, which is a specific function of dilatonic coupling vectors. The paper presents solutions for timelike and null circular geodesics that may play a crucial role in different astrophysical scenarios, including quasinormal modes of various test fields in the eikonal approximation. For $a = 1/2, 1, 3/2, 2$, the radii of the innermost stable circular orbit are presented and analyzed.