Photon Sphere for a Dilatonic Dyonic Black Hole in a Model with an Abelian Gauge Field and a Scalar Field
Ivashchuk V.D. Kayumov U.S. Malybayev A.N. Nurbakova G.S.
December 2025Pleiades Publishing
Gravitation and Cosmology
2025#31Issue 4591 - 599 pp.
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.
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Peoples’ Friendship University of Russia (RUDN University), ul. Miklukho-Maklaya 6, Moscow, 117198, Russian Federation
Center for Gravitation and Fundamental Metrology, SCAM Rostest, ul. Ozyornaya 46, Moscow, 119361, Russian Federation
Al-Farabi Kazakh National University, Al-Farabi avenue, 71, Almaty, 050040, Kazakhstan
Peoples’ Friendship University of Russia (RUDN University)
Center for Gravitation and Fundamental Metrology
Al-Farabi Kazakh National University
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