Light ring and the appearance of matter accreted by black holes

Vitor Cardoso; Francisco Duque; Arianna Foschi

doi:10.1103/physrevd.103.104044

Light ring and the appearance of matter accreted by black holes

Physical Review D ◽

10.1103/physrevd.103.104044 ◽

2021 ◽

Vol 103 (10) ◽

Author(s):

Vitor Cardoso ◽

Francisco Duque ◽

Arianna Foschi

Keyword(s):

Black Holes ◽

Light Ring

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Image of the thin accretion disk around compact objects in the Einstein–Gauss–Bonnet gravity

The European Physical Journal C ◽

10.1140/epjc/s10052-021-09624-5 ◽

2021 ◽

Vol 81 (10) ◽

Author(s):

Galin Gyulchev ◽

Petya Nedkova ◽

Tsvetan Vetsov ◽

Stoytcho Yazadjiev

Keyword(s):

Black Holes ◽

Accretion Disk ◽

Physical Mechanism ◽

Compact Object ◽

Ring Structure ◽

Compact Objects ◽

Schwarzschild Black Hole ◽

Naked Singularities ◽

Bonnet Gravity ◽

Light Ring

AbstractWe study the optical appearance of a thin accretion disk around compact objects within the Einstein–Gauss–Bonnet gravity. Considering static spherically symmetric black holes and naked singularities we search for characteristic signatures which can arise in the observable images due to the modification of general relativity. While the images of the Gauss–Bonnet black holes closely resemble the Schwarzschild black hole, naked singularities possess a distinctive feature. A series of bright rings are formed in the central part of the images with observable radiation $$10^3$$ 10 3 times larger than the rest of the flux making them observationally significant. We elucidate the physical mechanism, which causes the appearance of the central rings, showing that the image is determined by the light ring structure of the spacetime. In a certain region of the parametric space the Gauss–Bonnet naked singularities possess a stable and an unstable light ring. In addition the gravitational field becomes repulsive in a certain neighbourhood of the singularity. This combination of features leads to the formation of the central rings implying that the effect is not specific for the Einstein–Gauss–Bonnet gravity but would also appear for any other compact object with the same characteristics of the photon dynamics.

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Kerr Black Holes within a Modified Theory of Gravity

Universe ◽

10.3390/universe5090191 ◽

2019 ◽

Vol 5 (9) ◽

pp. 191 ◽

Cited By ~ 1

Author(s):

Peter O. Hess ◽

Enrique López-Moreno

Keyword(s):

Black Holes ◽

Black Hole ◽

Event Horizon ◽

Kerr Black Hole ◽

Standard Theory ◽

Vacuum Fluctuations ◽

Modified Theory Of Gravity ◽

Theory Of Gravity ◽

Modified Theory ◽

Light Ring

The Kerr black hole is studied within a modified theory of gravity, which adds the effects of vacuum fluctuations near a black hole. These vacuum fluctuations are treated as a dark energy. A parameter is introduced to account for these fluctuations. It is zero for the standard theory and acquires a maximal value, just before there would be no event horizon. The existence of an event horizon not only depends on the value of this parameter, but also on the spin of the black hole. In addition, we study the existence of a light-ring. We also elaborate on the relation of the appearance and vanishing of the event horizon and light-ring to phase transitions.

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