Shadows and photon spheres with spherical accretions in the four-dimensional Gauss–Bonnet black hole

Abstract

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.

Holographic superconductors in 4D Einstein-Gauss-Bonnet gravity

“…Interestingly, the solution of the same form has been presented in the conformal anomaly inspired gravity [40,41]. Along this line, the Einstein-Gauss-Bonnet gravity in the 4D spacetime has been explored extensively on various aspects, including the exact solutions [42][43][44][45][46][47][48][49][50][51][52][53][54][55], the quasinormal modes and stability [56][57][58][59][60][61][62][63][64][65][66][67], the observable shadows [68][69][70][71][72][73], the geodesics and gravitational lensing [74][75][76][77][78], and the thermodynamics and cosmic censorship conjecture [79][80][81][82][83][84][85][86].…”

Observational appearances of a f(R) global monopole black hole illuminated by various accretions

“…In this case, the optical appearance of shadow with two photon spheres in a Hairy Black Hole has been presented in [78], where the smaller photon sphere is considered to be the shadow boundary. For another model of accretion, namely the optically thin and geometrically thin disk, the later studies [79][80][81][82][83][84][85][86][87] show that the size of shadow is closely related to the position of the accretion, and the bright region outside of shadow are always composed of direct emission, lensing rings and photon rings. With this consideration, an optically observational signature of the asymmetric thin-shell wormhole has been thoroughly investigated, which shows that this signature can be used to distinguish wormholes from black holes [88].…”

Tidal effects in 4D Einstein–Gauss–Bonnet black hole spacetime

“…The physical properties and the novel observable a e-mail: csb3752@hunnu.edu.cn (corresponding author) b e-mail: jljing@hunnu.edu.cn effects for these black hole solutions have been explored in Refs. [2][3][4][5][6][7]. However, there are also some criticisms on this theory of Gravity [8][9][10][11][12].…”