Shadow of a spinning black hole in an expanding universe

Li, Peng-Cheng; Guo, Minyong; Chen, Bin

doi:10.1103/physrevd.101.084041

Cited by 138 publications

(64 citation statements)

References 64 publications

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“…The dark interior is called a black hole shadow while the bright ring is called a photon ring. The shadow of a black hole is caused by gravitational light deflection [7][8][9][10][11]. Specifically, when light emitting from the accretion passes through the vicinity of the black hole toward the observer, its trajectory will be deflected.…”

Section: Introductionmentioning

confidence: 99%

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

2020

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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.

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Section: Introductionmentioning

confidence: 99%

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

2020

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“…It would also be very interesting to study how the results we obtained change when we relax these assumptions. As was discussed in [68], the shadow of a Kerr black hole can be obtained in a similar way as for a McVittie black hole, which we used in this paper. The shadow obtained by these authors is quite similar to those in McVittie, with two different angular sizes due to the black hole spin.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Black Hole Shadow Drift and Photon Ring Frequency Drift

Frion¹,

Giani²,

Miranda³

2021

TheOJA

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The apparent angular size of the shadow of a black hole in an expanding Universe is redshift-dependent. Since cosmological redshifts change with time -known as the redshift drift -all redshift-dependent quantities acquire a time dependence, and a fortiori so do black hole shadows. We find a mathematical description of the black hole shadow drift and show that the amplitude of this effect is of order 10 −16 per day for M87 . While this effect is small, we argue that its non-detection can be used to constrain the accretion rate around supermassive black holes, as well as a novel probe of the equivalence principle. If general relativity is assumed, we infer from the data obtained by the Event Horizon Telescope for M87 a maximum accretion rate of |Ṁ /M | ≤ 10 5 M per year. On the other hand, in the case of an effective gravitation coupling, we derive a constraint of |Ġ/G| ≤ 10 −3 − 10 −4 per year. The effect of redshift drift on the visibility amplitude and frequency of the universal interferometric signatures of photon rings is also discussed, which we show to be very similar to the shadow drift. This is of particular interest for future experiments involving spectroscopic and interferometric techniques, which could make observations of photon rings and their frequency drifts viable. INTRODUCTIONRedshift is an omnipresent Doppler-effect-related quantity, used in cosmology to build meaningful spatial and temporal distances. In 1962, Sandage and McVittie [1, 2] showed that the redshift is in fact a dynamical quantity, with a time derivativė z, referred to as redshift drift. A redshift drift driven by the expansion of the Universe is called a cosmological drift , with the interesting consequence of turning redshift-dependent quantities into time-dependent ones. The cosmological drift depends on the Hubble rate H(z), and is expected to be very small at low redshift z, with a redshift change of the order of 10 −10 per year. However, it applies to every object in the Universe, which makes all of them possible probes of the drift, and collaborations such as the Extremely Large Telescope [4], the Square-Kilometer Array [5] or the Vera C. Rubin Observatory [6] will provide means of its detection. Optimistic estimates show that these facilities could reach a precision of 10 −10 , for example with monitoring programs of 1000 hours of exposure with a 40-meter telescope [7]. For this reason, cosmology with redshift drifts is an active field of research [8][9][10][11][12][13][14][15][16][17][18][19][20], which we advance further with this work, in which we investigate how the cosmological drift would affect the image from black hole shadows and interferometric signatures from black holes' photon rings.Black holes were first predicted over a century ago, yet the first direct image of a black hole was reconstructed only very recently by the Event Horizon Telescope (EHT) collaboration [21][22][23][24][25][26][27]. The direct detection of the shadow of M87 , the supermassive black hole at the centre of the galaxy Messier 87, suggest...

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“…The observer can not be set at the spatial infinite. In this situation, we introduce orthonormal tetrads for observers located at finite distance, zero-angular-momentobservers (ZAMOs) reference frame [18], which has been used in the study of black hole shadow in de Sitter spacetime [74][75][76]. In this way, we assume that the static observer is locally at (r obs , θ obs ) in the Boyer-Lindquist coordinates.…”

Section: The Spacetime Of Schwarzschild Black Hole Perturbed By Gravitational Wave and Null Geodesicsmentioning

confidence: 99%

Effect of gravitational wave on shadow of a Schwarzschild black hole

2021

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We have studied the shadows of a Schwarzschild black hole under a special polar gravitational perturbation, which is a particular solution of Einstein equations expanded up to first order. It is shown that the black hole shadow changes periodically with time and the change of shadow depends on the Legendre polynomial order parameter l and the frequency $$\sigma $$ σ of gravitational wave. For the odd order of Legendre polynomial, the center of shadow oscillates along the direction which is vertical to equatorial plane. For even l, the center of shadow does not move, but the shadow alternately stretches and squeezes with time along the vertical direction. Moreover, the presence of the gravitational wave leads to the self-similar fractal structures appearing in the boundary of the black hole shadow. We also find that this special gravitational wave has a greater influence on the vertical direction of black hole shadow.

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Shadow of a spinning black hole in an expanding universe

Cited by 138 publications

References 64 publications

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

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

Black Hole Shadow Drift and Photon Ring Frequency Drift

Effect of gravitational wave on shadow of a Schwarzschild black hole

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