Event Horizon Image within Black Hole Shadow

Dokuchaev, V. I.; Nazarova, Natalia O.

doi:10.1134/s1063776119030026

Cited by 32 publications

(29 citation statements)

References 57 publications

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“…Loosely speaking the black hole shadow is due to strong gravitational lensing effect [30][31][32][33][34][35][36][37][38][39][40][41], near the photon sphere, which is defined as the set of directions in the observer's sky, from which no signal from distant source reaches the observer. This effect can in principle be observed from Earth, providing a definitive test of existence of black holes and for this very purpose, the Event Horizon telescope is being designed to observe the shadow like structure around the supermassive object at the center of our galaxy [42][43][44][45]. Various other interesting aspects of photon sphere and shadow has been extensively studied by numerous authors [46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62].…”

Section: Introductionmentioning

confidence: 99%

Understanding photon sphere and black hole shadow in dynamically evolving spacetimes

2019

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We have derived the differential equation governing the evolution of the photon sphere for dynamical black hole spacetimes with or without spherical symmetry. Numerical solution of the same depicting evolution of the photon sphere has been presented for Vaidya, Reissner-Nordström-Vaidya and de-Sitter Vaidya spacetimes. It has been pointed out that evolution of the photon sphere depends crucially on the validity of the null energy condition by the in-falling matter and may present an observational window to even test it through black hole shadow. We have also presented the evolution of the photon sphere for slowly rotating Kerr-Vaidya spacetime and associated structure of black hole shadow. Finally, the effective graviton metric for Einstein-Gauss-Bonnet gravity has been presented, and the graviton sphere has been contrasted with the photon sphere in this context. * akash.mishra@iitgn.ac.in

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Section: Introductionmentioning

confidence: 99%

Understanding photon sphere and black hole shadow in dynamically evolving spacetimes

2019

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“…Parameters of these two photon trajectories are λ 1 = −0.047 and q 1 = 2.19 and, respectively, λ 2 = −0.029 and q 2 = 1.52. Note, that the dark event horizon silhouettes, similar to ones in Figures 7-10, were reproduced during many years in numerical modeling of accretion disks with the inner edge at the black hole event horizon (see, e.g., [167,[274][275][276][277][278][279][280][281][282][283][284][285][286][287]). Figure 11 demonstrates a numerical model for the gravitational lensing of a compact star, falling into the fast rotating black hole SgrA* (a = 0.9982) and observed in discrete time intervals by a distant static observer, placed a little bit above the equatorial plane.…”

Section: Figurementioning

confidence: 86%

Visible Shapes of Black Holes M87* and SgrA*

Dokuchaev

Nazarova

2020

Universe

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We review the physical origins for possible visible images of the supermassive black hole M87* in the galaxy M87 and SgrA* in the Milky Way Galaxy. The classical dark black hole shadow of the maximal size is visible in the case of luminous background behind the black hole at the distance exceeding the so-called photon spheres. The notably smaller dark shadow (dark silhouette) of the black hole event horizon is visible if the black hole is highlighted by the inner parts of the luminous accreting matter inside the photon spheres. The first image of the supermassive black hole M87*, obtained by the Event Horizon Telescope collaboration, shows the lensed dark image of the southern hemisphere of the black hole event horizon globe, highlighted by accreting matter, while the classical black hole shadow is invisible at all. A size of the dark spot on the Event Horizon Telescope (EHT) image agrees with a corresponding size of the dark event horizon silhouette in a thin accretion disk model in the case of either the high or moderate value of the black hole spin, a≳0.75.

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“…Similarly to the case of massive test particles, there exist two kinds of null geodesics in a wormhole spacetime: a geodesic of the first kind passes through the wormhole throat, while a geodesic of the second kind remains in the region r ≥ 0. A null geodesic is of the first kind if and only if the condition (27) holds. Geodesics of the first kind (second kind) are shown in the left panel (respectively, right panel) of Figures 5 and 6.…”

Section: Trajectories Of Null Geodesicsmentioning

confidence: 99%

“…Then the image of a wormhole, that is, the shape and brightness of the wormhole accretion disk, is determined by the behaviour of null geodesics of both these kinds, together with the inclination of the disk plane with respect to the line of sight of an observer. In general, an analytical computation of this image for scalar field wormholes seems to be impossible, therefore we will briefly discuss these issues qualitatively in the same standard manner as for black holes [4,7,14,17,26,27].…”

Section: Trajectories Of Null Geodesicsmentioning

confidence: 99%

“…This approach allows us to explore some unevident features of the trajectories of massive and massless test particles in such spacetimes; these features are usually hidden in qualitative models based on computer simulations. Other useful fully analytical models are based on the Kerr-like configurations, which, however, do not take account of dark matter [4,26,27]. We will consider the simplest case of a spherically symmetric, static, traversable wormhole supported by a nonlinear self-gravitating minimally coupled phantom (in another terminology, ghost) scalar field with an arbitrary self-interaction potential.…”

Section: Introductionmentioning

confidence: 99%

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Null and Timelike Geodesics near the Throats of Phantom Scalar Field Wormholes

2020

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We study geodesic motion near the throats of asymptotically flat, static, spherically symmetric traversable wormholes supported by a self-gravitating minimally coupled phantom scalar field with an arbitrary self-interaction potential. We assume that any such wormhole possesses the reflection symmetry with respect to the throat, and consider only its observable “right half”. It turns out that the main features of bound orbits and photon trajectories close to the throats of such wormholes are very different from those near the horizons of black holes. We distinguish between wormholes of two types, the first and second ones, depending on whether the redshift metric function has a minimum or maximum at the throat. First, it turns out that orbits located near the centre of a wormhole of any type exhibit retrograde precession, that is, the angle of pericentre precession is negative. Second, in the case of high accretion activity, wormholes of the first type have the innermost stable circular orbit at the throat while those of the second type have the resting-state stable circular orbit in which test particles are at rest at all times. In our study, we have in mind the possibility that the strongly gravitating objects in the centres of galaxies are wormholes, which can be regarded as an alternative to black holes, and the scalar field can be regarded as a realistic model of dark matter surrounding galactic centres. In this connection, we discuss qualitatively some observational aspects of results obtained in this article.

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Event Horizon Image within Black Hole Shadow

Cited by 32 publications

References 57 publications

Understanding photon sphere and black hole shadow in dynamically evolving spacetimes

Understanding photon sphere and black hole shadow in dynamically evolving spacetimes

Visible Shapes of Black Holes M87* and SgrA*

Null and Timelike Geodesics near the Throats of Phantom Scalar Field Wormholes

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