Strong deflection lensing by charged black holes in scalar–tensor gravity

Eiroa, Ernesto F.; Sendra, Carlos M.

doi:10.1140/epjc/s10052-014-3171-1

Cited by 29 publications

(16 citation statements)

References 79 publications

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“…In addition, it will allow one to set constraints on the validity of alternative theories of gravity which also predict black holes and corresponding shadows (see e.g. Eiroa & Sendra 2014;Tsukamoto et al 2014;Falcke & Markoff 2013).…”

Section: Introductionmentioning

confidence: 99%

A coordinate-independent characterization of a black hole shadow

Abdujabbarov

Rezzolla

Ahmedov

2015

Mon. Not. R. Astron. Soc.

223

140

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A large international effort is under way to assess the presence of a shadow in the radio emission from the compact source at the centre of our Galaxy, Sagittarius A * (Sgr A * ). If detected, this shadow would provide the first direct evidence of the existence of black holes and that Sgr A * is a supermassive black hole. In addition, the shape of the shadow could be used to learn about extreme gravity near the event horizon and to determine which theory of gravity better describes the observations. The mathematical description of the shadow has so far used a number of simplifying assumptions that are unlikely to be met by the real observational data. We here provide a general formalism to describe the shadow as an arbitrary polar curve expressed in terms of a Legendre expansion. Our formalism does not presume any knowledge of the properties of the shadow, e.g., the location of its centre, and offers a number of routes to characterize the distortions of the curve with respect to reference circles. These distortions can be implemented in a coordinate independent manner by different teams analysing the same data. We show that the new formalism provides an accurate and robust description of noisy observational data, with smaller error variances when compared to previous approaches for the measurement of the distortion.

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Section: Introductionmentioning

confidence: 99%

A coordinate-independent characterization of a black hole shadow

Abdujabbarov

Rezzolla

Ahmedov

2015

Mon. Not. R. Astron. Soc.

223

140

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“…In the RN black hole spacetimes the photon motion and the gravitational lensing were studied in[49,16,46,18]. In similar braneworld black hole spacetimes the optical effects were studied in[43,44,36,1].…”

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confidence: 99%

Gravitational lensing and ghost images in the regular Bardeen no-horizon spacetimes

Schee

Stuchlík

2015

J. Cosmol. Astropart. Phys.

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We study deflection of light rays and gravitational lensing in the regular Bardeen no-horizon spacetimes. Flatness of these spacetimes in the central region implies existence of interesting optical effects related to photons crossing the gravitational field of the no-horizon spacetimes with low impact parameters. These effects occur due to existence of a critical impact parameter giving maximal deflection of light rays in the Bardeen no-horizon spacetimes. We give the critical impact parameter in dependence on the specific charge of the spacetimes, and discuss "ghost" direct and indirect images of Keplerian discs, generated by photons with low impact parameters. The ghost direct images can occur only for large inclination angles of distant observers, while ghost indirect images can occur also for small inclination angles. We determine the range of the frequency shift of photons generating the ghost images and determine distribution of the frequency shift across these images. We compare them to those of the standard direct images of the Keplerian discs. The difference of the ranges of the frequency shift on the ghost and direct images could serve as a quantitative measure of the Bardeen no-horizon spacetimes. The regions of the Keplerian discs giving the ghost images are determined in dependence on the specific charge of the no-horizon spacetimes. For comparison we construct direct and indirect (ordinary and ghost) images of Keplerian discs around Reissner-Nördström naked singularities demonstrating a clear qualitative difference to the ghost direct images in the regular Bardeen no-horizon spacetimes. The optical effects related to the low impact parameter photons thus give clear signature of the regular Bardeen no-horizon spacetimes, as no similar phenomena could occur in the black hole or naked singularity spacetimes. Similar direct ghost images have to occur in any regular no-horizon spacetimes having nearly flat central region.

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“…In the weak deflection limit we may assume that the light ray is given by r(t) = b/ sin ϕ at zeroth order, using ( 12) and (15) for the deflection angle one finds…”

Section: Optical Curvature and The Deflection Anglementioning

confidence: 99%

“…This phenomena has been studied in details in various astrophysical aspects, both in the weak limit [2,3] and strong limit approximation [4][5][6]. In the last few years, there has been a growing interest in studying weak as well as strong field, along this line of research many papers have been written, including, the naked singularities and relativistic images of Schwarzschild black hole lensing, role of the scalar field in gravitational lensing, [7][8][9], wormholes [10], to test the cosmic censorship hypothesis [11], gravitational lensing from charged black holes in the weak field limit [12], Kerr black hole lensing [13], gravitational lensing by massless braneworld black holes [14], strong deflection lensing by charged black holes in scalar-tensor gravity [15], and the references therein.…”

Section: Introductionmentioning

confidence: 99%

Light deflection with torsion effects caused by a spinning cosmic string

Jusufi

2016

Eur. Phys. J. C

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Using a new geometrical method introduced by Werner, we find the deflection angle in the weak limit approximation by a spinning cosmic string in the context of the Einstein-Cartan (EC) theory of gravity. We begin by adopting the String-Randers optical metric, then we apply the Gauss-Bonnet theorem to the optical geometry and derive the leading terms of the deflection angle in the equatorial plane. Calculation shows that light deflection is affected by the intrinsic spin of the cosmic string and torsion.

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Strong deflection lensing by charged black holes in scalar–tensor gravity

Cited by 29 publications

References 79 publications

A coordinate-independent characterization of a black hole shadow

A coordinate-independent characterization of a black hole shadow

Gravitational lensing and ghost images in the regular Bardeen no-horizon spacetimes

Light deflection with torsion effects caused by a spinning cosmic string

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