Photon Sphere for a Dilatonic Dyonic Black Hole in a Model with an Abelian Gauge Field and a Scalar Field

Abstract: A dilatonic dyonic black hole solution with the gravitational radius and two charges and (electric and magnetic ones) is considered in a gravitational 4D model with one scalar field and one 2-form, with the dilatonic coupling constant. Circular null geodesics are explored. The 3rd order polynomial master equation for the radius of photon sphere is studied. There is only one solution with. The circular null geodesics are shown to be unstable. The black hole shadow is studied, and relations for the shadow angle and critical impact parameter are obtained. © Pleiades Publishing, Ltd. 2025.