Gravastar Shadows

  title={Gravastar Shadows},
  author={Nobuyuki Sakai and Hiromi Saida and Takashi Tamaki},
Direct observation of black holes is one of the grand challenges in astronomy. If there are supercompact objects which possess unstable circular orbits of photons, however, it may be difficult to distinguish them from black holes by observing photons. As a model of super-compact objects, we consider a gravastar (gravitational-vacuum-star) which was originally proposed by Mazur and Mottola. For definiteness, we adopt a spherical thin-shell model of a gravastar developed by Visser and Wiltshire… 
Observational signatures of strongly naked singularities: image of the thin accretion disk
We study the optical appearance of a thin accretion disk around the strongly naked static Janis-Newman-Winicour singularity. The solution does not possess a photon sphere, which results in the
Chaotic photon orbits and shadows of a non-Kerr object described by the Hartle–Thorne spacetime
The data from the event horizon telescope have provided a novel view of the vicinity of the horizon of a black hole (BH), by imaging the region around the light-ring. They have also raised hopes for
Study of gravastars in Rastall gravity
Gravastars have been considered as a feasible alternative to black holes in the past couple of decades. Stable models of gravastar have been studied in many of the alternative gravity theories
Photon ring structure of rotating regular black holes and no-horizon spacetimes
The Kerr black holes possess a photon region with prograde and retrograde orbits radii, respectively, M⩽rp−⩽3M and 3M⩽rp+⩽4M , and thereby always cast a closed photon ring or a shadow silhouette for
Polarized image of equatorial emission in horizonless spacetimes I: traversable wormholes
We study the linear polarization from the accretion disk around a class of static traversable wormholes. Applying the simplified model of a magnetized fluid ring orbiting in the equatorial plane, we
Shadow of a naked singularity
We analyze the redshift suffered by photons originating from an external source, traversing a collapsing dust cloud and finally being received by an asymptotic observer. In addition, we study the
Shadows around the q-metric
One crucial problem in relativistic astrophysics is that of the nature of black hole candidates. It is usually assumed that astrophysical black holes are described by the Schwarzschild or Kerr
Shadows of spherically symmetric black holes and naked singularities
We compare shadows cast by Schwarzschild black holes with those produced by two classes of naked singularities that result from gravitational collapse of spherically symmetric matter. The latter
Testing general relativity with the Event Horizon Telescope
  • D. Psaltis
  • Physics
    General Relativity and Gravitation
  • 2019
The Event Horizon Telescope is a millimeter VLBI array that aims to take the first pictures of the black holes in the center of the Milky Way and of the M87 galaxy, with horizon scale resolution.
Spherical polytropic balls cannot mimic black holes
The so-called black hole shadow is a dark region which is expected to appear in a fine image of optical observation of black holes. It is essentially an absorption cross section of black hole, and


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