Fundamental photon orbits: Black hole shadows and spacetime instabilities

Cunha, Pedro V. P.; Herdeiro, Carlos; Radu, Eugen

doi:10.1103/physrevd.96.024039

Cited by 169 publications

(199 citation statements)

References 38 publications

Supporting

Mentioning

193

Contrasting

Unclassified

Order By: Relevance

“…which is exactly a property of the photon region of Kerr-like solutions, as well as the general property of spheroidal photon orbits [41], representing a special case of fundamental photon orbits [42].…”

Section: Generalized Photon Regionmentioning

confidence: 99%

“…Altogether spherical orbits now will a three-dimensional photon region (PR) [37][38][39], which can be regarded as "thickened" photon sphere. Note that the closed photon orbits may exist in more general spacetimes in which case the name of fundamental or/and spheroidal photon orbits was suggested [40][41][42].More general trapping surfaces, proposed in [43] and further studied in [44], were called transversely trapping surfaces (TTS). In Schwarzschild case TTS are the spheres with the radii r ≤ 3M .…”

mentioning

confidence: 99%

See 1 more Smart Citation

Photon trapping in static axially symmetric spacetime

Gal’tsov

Kobialko

2019

Phys. Rev. D

View full text Add to dashboard Cite

Recently, several new characteristics have been introduced to describe null geodesic structure of strong gravitational field, such as photon regions, transversely trapping surfaces and some generalizations. They give an alternative and concise way to describe lensing and shadow features of compact objects with strong gravitational field without recurring to complete integration of the geodesic equations. Here we test this construction in the case of the Weyl metrics when geodesic equations are non-separable, and thus can not be integrated analytically, while the above characteristic surfaces and regions can be described in a closed form. We develop further our formalism for a class of static axially symmetric spacetimes introducing more detailed specification of transversely trapping surfaces in terms of their principal curvatures. Surprisingly, we find in the static case without spherical symmetry certain features, such as photon regions, previously known in the Kerr space. These photon regions can be regarded as photon spheres, "thickened" due to oblateness of the metric.including the dilaton field [34]).Meanwhile, in the stationary spacetimes photon surfaces generically do not exist, being, in some sense, disintegrated by rotation. The Taub-NUT metric, though belongs to this class, is an exception, whose existence is explained by local SO(3) symmetry which is preserved. In the Kerr metric the circular photon orbits exist in the equatorial plane [35]. Non-equatorial orbits with constant Boyer-Lindquist radii no longer belong to any plane, but lie on the surface of a sphere instead ("spherical photon orbits" [36]). But such surfaces are not photon spheres, which by definition should be densely filled. In the Kerr case every spherical orbit corresponds to certain value of the impact parameter defined as ratio of the angular momentum to the energy. Altogether spherical orbits now will a three-dimensional photon region (PR) [37][38][39], which can be regarded as "thickened" photon sphere. Note that the closed photon orbits may exist in more general spacetimes in which case the name of fundamental or/and spheroidal photon orbits was suggested [40][41][42].More general trapping surfaces, proposed in [43] and further studied in [44], were called transversely trapping surfaces (TTS). In Schwarzschild case TTS are the spheres with the radii r ≤ 3M . These are defined as surfaces such that initially tangent photons either remain in them or move inward; these do exist in Kerr and more general stationary axially symmetric metrics.The totality of TTSs form a three-dimensional region (TTR), which apparently will be invisible if one looks at the Schwarzschild black hole illuminated from behind. Further generalizations suggested in [44] include partial TTS (PTTS) which are non-closed surfaces (contrary to the definition in [43]) of the shape of a spherical cap. Finally, it is reasonable to introduce anti-TTS and PTTS (abbreviated as ATTS and APPTS, the corresponding regions -TTR and PTTR respoctively) replacing inward to outwa...

show abstract

Section: Generalized Photon Regionmentioning

confidence: 99%

mentioning

confidence: 99%

Photon trapping in static axially symmetric spacetime

Gal’tsov

Kobialko

2019

Phys. Rev. D

View full text Add to dashboard Cite

show abstract

“…LRs are bound planar photon orbits (see [35] for a general discussion of bound photon orbits). Their existence around a compact object implies strong lensing effects.…”

Section: Lensingmentioning

confidence: 99%

Lensing and dynamics of ultracompact bosonic stars

et al. 2017

Self Cite

View full text Add to dashboard Cite

Spherically symmetric bosonic stars are one of the few examples of gravitating solitons that are known to form dynamically, via a classical process of (incomplete) gravitational collapse. As stationary solutions of the Einstein-Klein-Gordon or the Einstein-Proca theory, bosonic stars may also become sufficiently compact to develop light rings and hence mimic, in principle, gravitational-wave observational signatures of black holes (BHs). In this paper, we discuss how these horizonless ultracompact objects (UCOs) are actually distinct from BHs, both phenomenologically and dynamically. In the electromagnetic channel, the light ring associated phenomenology reveals remarkable lensing patterns, quite distinct from a standard BH shadow, with an infinite number of Einstein rings accumulating in the vicinity of the light ring, both inside and outside the latter. The strong lensing region, moreover, can be considerably smaller than the shadow of a BH with a comparable mass. Dynamically, we investigate the fate of such UCOs under perturbations, via fully nonlinear numerical simulations and observe that, in all cases, they decay into a Schwarzschild BH within a time scale of OðMÞ, where M is the mass of the bosonic star. Both these studies reinforce how difficult it is for horizonless UCOs to mimic BH phenomenology and dynamics, in all its aspects.

show abstract

“…The unstable spherical orbits located in the impact parameter space after the intersection point A do not influence the shadow. Yet, they have impact on the lensing properties of the spacetime, as observed in [42].…”

Section: Figmentioning

confidence: 99%

“…They arise at the junction of the curves determined from the two families of spherical orbits due to a non-smooth merger of the two branches. While it was anticipated in [42,43] that the cusps result from the interplay between stable and unstable spherical photon orbits, we provide for our solution the explicit mechanism for their formation. For an equatorial observer, we investigate the behavior of the cusps when varying the angular momentum proving that a critical spin parameter exists for which they disappear.…”

Section: Introductionmentioning

confidence: 99%

On the shadow of rotating traversable wormholes

et al. 2018

View full text Add to dashboard Cite

We revisit the shadow of rotating traversable wormholes discussing the role of the wormhole throat in the shadow formation. For certain classes of wormholes the throat serves as a potential barrier for light rays with particular impact parameters, thus modifying the shadow shape. We consider a couple of wormhole solutions and examine the structure of their shadow images, and the intrinsic mechanisms for their formation. Some of the shadows possess cuspy edges, which arise due to the interplay of two distinct families of unstable spherical orbits. These solutions provide examples, in which the explicit mechanism for cusp formation can be uncovered.

show abstract

Fundamental photon orbits: Black hole shadows and spacetime instabilities

Cited by 169 publications

References 38 publications

Photon trapping in static axially symmetric spacetime

Photon trapping in static axially symmetric spacetime

Lensing and dynamics of ultracompact bosonic stars

On the shadow of rotating traversable wormholes

Contact Info

Product

Resources

About