Regular Article – Theoretical Physics
Shadows and photon spheres with spherical accretions in the four-dimensional Gauss–Bonnet black hole
State Key Laboratory of Mountain Bridge and Tunnel Engineering, Chongqing Jiaotong University, 400074, Chongqing, China
2 Department of Mechanics, Chongqing Jiaotong University, 400074, Chongqing, China
3 Department of Space Science, Center for Gravitational Physics, Beihang University, 100191, Beijing, China
4 International Research Institute for Multidisciplinary Science, Beihang University, 100191, Beijing, China
5 Department of Physics, Beijing Normal University, 100875, Beijing, China
6 Theoretische Natuurkunde, Vrije Universiteit Brussel, and The International Solvay Institutes, Pleinlaan 2, 1050, Brussels, Belgium
Accepted: 8 September 2020
Published online: 21 September 2020
We investigate the shadows and photon spheres of the four-dimensional Gauss–Bonnet black hole with the static and infalling spherical accretions. We show that, for both cases, there always exist shadows and photon spheres. The radii of the shadows and photon spheres are independent of the profiles of accretion for a fixed Gauss–Bonnet constant, implying that the shadow is a signature of the spacetime geometry and it is hardly influenced by accretion. Because of the Doppler effect, the shadows of the infalling accretion are found to be darker than in the static case. We also investigate the effect of the Gauss–Bonnet constant on the shadow and photon spheres, and we find that the larger the Gauss–Bonnet constant is, the smaller the radii of the shadow and photon spheres will be. In particular, the observed specific intensity increases as the Gauss–Bonnet constant grows.
© The Author(s) 2020
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