Stability analysis of circular geodesics in dyonic dilatonic black hole spacetimes

This research examines a non-extremal dyonic-like dilatonic charged black hole solution within a four-dimensional gravity model. The model includes two scalar (dilaton) fields and two Abelian vector fields, with interactions between them mediated by exponential terms involving two dilatonic coupling vectors. The solution is characterized by a dimensionless parameter a (where 0<a<2), which is explicitly defined as a function of the dilatonic coupling vectors. The paper also explores solutions for timelike and null circular geodesics, which are essential for understanding various astrophysical phenomena, including quasinormal modes of different test fields in the eikonal approximation. For all values of a, the innermost stable circular orbit (ISCO) is determined by reducing the problem to solving a fourth-order polynomial equation. © 2025 Elsevier B.V.