Imaging a non-singular rotating black hole at the center of the Galaxy

Lamy, Frédéric; Gourgoulhon, Éric; Paumard, T.; Vincent, F.

doi:10.1088/1361-6382/aabd97

Cited by 70 publications

(61 citation statements)

References 37 publications

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“…In this section we consider the rotating wormhole solution first described in Lamy et al (2018), which we hereafter refer to as Lamy wormhole. This solution was found by generalizing the spherically symmetric regular (i.e., singularity-free) black hole solution of Hayward (2006) to the rotating case.…”

Section: Lamy Spinning Wormholementioning

confidence: 99%

Geometric modeling of M87* as a Kerr black hole or a non-Kerr compact object

Vincent

Wielgus

Abramowicz

et al. 2021

A&A

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Context. The Event Horizon Telescope (EHT) collaboration recently obtained the first images of the surroundings of the supermassive compact object M87* at the center of the galaxy M87. This provides a fascinating probe of the properties of matter and radiation in strong gravitational fields. It is important to determine from the analysis of these results what can and cannot be inferred about the nature of spacetime around M87* Aims. We want to develop a simple analytic disk model for the accretion flow of M87*. Compared to general-relativistic magnetohydrodynamic models, this new approach has the advantage that it is independent of the turbulent character of the flow and is controlled by only a few easy-to-interpret, physically meaningful parameters. We want to use this model to predict the image of M87*, assuming that it is either a Kerr black hole or an alternative compact object. Methods. We computed the synchrotron emission from the disk model and propagate the resulting light rays to the far-away observer by means of relativistic ray tracing. Such computations were performed assuming different spacetimes, such as Kerr, Minkowski, nonrotating ultracompact star, rotating boson star, or Lamy spinning wormhole. We performed numerical fits of these models to the EHT data. Results. We discuss the highly lensed features of Kerr images and show that they are intrinsically linked to the accretion-flow properties and not only to gravitation. This fact is illustrated by the notion of the secondary ring, which we introduce. Our model of a spinning Kerr black hole predicts mass and orientation consistent with the EHT interpretation. The non-Kerr images result in a similar quality of numerical fits and may appear very similar to Kerr images, once blurred to the EHT resolution. This implies that a strong test of the Kerr spacetime may be out of reach with the current data. We note that future developments of the EHT could alter this situation. Conclusions. Our results show the importance of studying alternatives to the Kerr spacetime to be able to test the Kerr paradigm unambiguously. More sophisticated treatments of non-Kerr spacetimes and more advanced observations are needed to proceed further in this direction.

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Section: Lamy Spinning Wormholementioning

confidence: 99%

Geometric modeling of M87* as a Kerr black hole or a non-Kerr compact object

Vincent

Wielgus

Abramowicz

et al. 2021

A&A

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“…Generic regular NED black holes were introduced in [25,61]. Along with the static and spherically symmetric non-rotating solutions, generalizations to the rotating spacetimes were derived and studied extensively [34,59]. It is thus of crucial importance to look for clear observational signatures of the regular black holes.…”

Section: Introductionmentioning

confidence: 99%

Shadow of the regular Bardeen black holes and comparison of the motion of photons and neutrinos

2019

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The aim of the present research is the analysis of the photon motion in the regular spacetimes arising as solutions of the Einstein gravity coupled with a non-linear electrodynamics (NED). The photons no longer follow the null geodesic of the background spacetime, but the null geodesics of an effective geometry where the electromagnetic nonlinearity is directly reflected in addition to the spacetime geometry. Motion of photons is compared to the motion of neutrinos that are not directly affected by the non-linearities of a non-Maxwellian electromagnetic field, and follow null geodesics of the background spacetime. We determine shadows of the regular Bardeen black holes, representing a special solution of the general relativity coupled with NED related to a magnetic charge, both for photons and neutrinos, and compare them to the shadow of the related Reissner-Nordstrom black holes. We demonstrate that the direct NED effects give clear signature of the presence of the regular black holes, on the level going up to 20% that is detectable by recent observational techniques. We also demonstrate strong influence of the NED effects on deflection angle of photons moving in the Bardeen spacetimes, and on the time delay of the motion of photons and neutrinos in vicinity of the black hole horizon.

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“…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%

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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Imaging a non-singular rotating black hole at the center of the Galaxy

Cited by 70 publications

References 37 publications

Geometric modeling of M87* as a Kerr black hole or a non-Kerr compact object

Geometric modeling of M87* as a Kerr black hole or a non-Kerr compact object

Shadow of the regular Bardeen black holes and comparison of the motion of photons and neutrinos

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

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