Аңдатпа
Dilatonic dyon-like black hole solutions with two (color) charges $$Q_{1}$$ and $$Q_{2}$$ (electric and magnetic ones) are considered in a gravitational 4D model with two scalar fields and two 2-forms. Two-dimensional dilatonic coupling vectors $$\vec{\lambda}_{i}$$ , $$i=1,2$$ , determining the model, obey the relation $$\vec{\lambda}_{1}\vec{\lambda}_{2}=1/2$$ . Circular null geodesics in the field of such black holes are explored. The master equation for the photon sphere radius $$R$$ is derived. A conjecture is suggested on the existence and uniqueness of the solution to the master equation with $$R>R_{g}$$ , where $$R_{g}$$ is the horizon radius. This conjecture is varified for certain special cases, e.g., for a charge symmetric configuration: $$Q_{1}^{2}=Q_{2}^{2}$$ . In this charge symmetric case, we present a relation for the spectrum of quasinormal modes of a test massless scalar field in the eikonal approximation, and an example of circular orbits of a massive particle.