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arXiv · 2603.19505

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

V. D. Ivashchuk·U. S. Kayumov·A. N. Malybayev·G. S. Nurbakova
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Abstract

Dilatonic dyon black hole solution with gravitational radius $2 \mu$ and two charges $Q_1$ and $Q_2$ (electric and magnetic ones) in the gravitational $4d$ model with one scalar field and one 2-form is considered. Dilatonic coupling constant $\lambda$ obeys $\lambda^2 = \frac{1}{2}$. The circular orbits for null geodesics are explored. The 3rd order polynomial master equation for radius $R_0$ of photon sphere is studied. It has only one solution which obeys $R_0 > 2 \mu$. The circular null geodesics are shown to be unstable. The black hole shadow is studied and relations for shadow angle and critical impact parameter are obtained.

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V. D. Ivashchuk, U. S. Kayumov, A. N. Malybayev, G. S. Nurbakova. 2026-03-19. Photon Sphere for a Dilatonic Dyonic Black Hole in a Model with an Abelian Gauge Field and a Scalar Field. https://doi.org/10.1134/s0202289325700471

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