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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

Abstract

Dilatonic dyon black hole solution with gravitational radius $2 μ$ 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 $λ$ obeys $λ^2 = \frac{1}{2}$. 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 $R_0 > 2 μ$. 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.

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

Abstract

Dilatonic dyon black hole solution with gravitational radius and two charges and (electric and magnetic ones) in the gravitational model with one scalar field and one 2-form is considered. Dilatonic coupling constant obeys . The circular orbits for null geodesics are explored. The 3rd order polynomial master equation for radius of photon sphere is studied. It has only one solution which obeys . 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.
Paper Structure (11 sections, 83 equations, 1 figure, 1 table)

This paper contains 11 sections, 83 equations, 1 figure, 1 table.

Table of Contents

  1. Introduction
  2. Black hole dyon solution
  3. Physical parameters
  4. Gravitational mass and scalar charge
  5. The Hawking temperature and entropy
  6. Circular geodesic solutions
  7. Geodesic equations
  8. Circular photon orbits
  9. Examples
  10. BH shadow
  11. Conclusions

Figures (1)

  • Figure 1: The function $F(x)$ from (\ref{['4.masteqx']}) for $p_1 = p_2 = 1$.