Revisiting the shadow of a black hole in the presence of a plasma

Huang, Yang; Dong, Yi-Ping; Liu, Daojun

doi:10.1142/s0218271818501146

Cited by 56 publications

(29 citation statements)

References 37 publications

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“…Several examples are worked out in the paper by Perlick and Tsupko [233], and several others, again for cases where the separability condition is satisfied, in a follow-up paper by Yan [234]. For some examples where the separability condition is not satisfied, the shadow was numerically calculated by Huang, Dong and Liu [235]. If the plasma frequency is not small in comparison to the frequency of the light, the shape of the shadow can be significantly different from the vacuum case.…”

Section: Influence Of a Plasma On The Shadowmentioning

confidence: 99%

Calculating black hole shadows: Review of analytical studies

Perlick,

Tsupko

2021

Preprint

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Example 2: Shadow in Reissner-Nordström space-time 9 Example 3: Shadow in Kottler space-time for static observer 9 IV. Shadow of a Kerr black hole 9 A. Calculation of the shadow for arbitrary position of the observer 9 B. Calculation of the shadow for an observer at large distance 13 C. Analytical properties of the shadow of a Kerr black hole 15 V. Generalization of the results for the Kerr space-time to other rotating black holes 17 VI. Shadows of wormholes and other compact objects that are not black holes 19 VII. The shadow of a collapsing star 21 VIII. Shadow in an expanding universe 21 A. Shadow in the Kottler space-time for comoving observers 22

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Section: Influence Of a Plasma On The Shadowmentioning

confidence: 99%

Calculating black hole shadows: Review of analytical studies

Perlick,

Tsupko

2021

Preprint

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“…where K = 12∆Mr s ∆r s (∆r s − 3M ) (26) −18M ∆M∆r 2 s + 3∆Mr 2 s (4∆r s + 3∆M) + ∆r 4 s . There are two photon spheres: the other one is given by the same equation (25), where K comes with an opposite sign in eq.…”

Section: Shadow Of a Black Hole Surrounded By Dark Mattermentioning

confidence: 99%

Shadow of a black hole surrounded by dark matter

2019

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We consider a simple spherical model consisting of a Schwarzschild black hole of mass M and a dark matter of mass ∆M around it. The general formula for the radius of black-hole shadow has been derived in this case. It is shown that the change of the shadow is not negligible, once the effective radius of the dark matter halo is of order ∼ √ 3M ∆M . For this to happen, for example, for the galactic black hole, the dark matter must be concentrated near the black hole. For small deviations from the Schwarzschild limit, the dominant contribution into the size of a shadow is due to the dark matter under the photon sphere, but at larger deviations, the matter outside the photon sphere cannot be ignored.

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“…The complete signature at EHT should be the combined information of the black hole shadow and the signal from the hot spot. In addition to the influence on the size and shape of a black hole discussed in [25,27], we find that there is a special segment of the shadow edge originating from the nearhorizon region and is approximately the same for both of the power-law-like models (18) and (19). Moreover, the image position and redshift of the hot spot are obviously influenced by the plasma as well.…”

Section: Introductionmentioning

confidence: 61%

“…The shadow for a Kerr black hole in a plasma has been studied in Refs. [23,25,27]. However, it is worth to revisit this for a high-spin black hole since doing so helps one to understand the image of a hot spot (and thus, the signature at EHT) better.…”

Section: Introductionmentioning

confidence: 99%

Influence of a plasma on the observational signature of a high-spin Kerr black hole

Yan

2019

Phys. Rev. D

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To approach a more reliable observational signature of a high-spin Kerr black hole, one should take into account the effects of its surroundings. To this end we study in this paper the influence of a surrounding plasma. We consider its refractive and dispersive effects on photon trajectories and ignore the gravitational effects of plasma particles as well as the absorption or scattering processes of photons. With two specific plasma models, we obtain analytical formulae for the black hole shadow and for the observational quantities of an orbiting "hot spot" seen by an observer located far away from the black hole. We find that the plasma has a frequency-dependent dispersive effect on the size and shape of the black hole shadow and on the image position and redshift of the hot spot. These results may be tested by the Event Horizon Telescope in the future.

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Revisiting the shadow of a black hole in the presence of a plasma

Cited by 56 publications

References 37 publications

Calculating black hole shadows: Review of analytical studies

Calculating black hole shadows: Review of analytical studies

Shadow of a black hole surrounded by dark matter

Influence of a plasma on the observational signature of a high-spin Kerr black hole

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