Photon rings of spherically symmetric black holes and robust tests of non-Kerr metrics

  title={Photon rings of spherically symmetric black holes and robust tests of non-Kerr metrics},
  author={Maciek Wielgus},
  journal={Physical Review D},
  • M. Wielgus
  • Published 22 September 2021
  • Physics
  • Physical Review D
Under very general assumptions on the accretion flow geometry, images of a black hole illuminated by electromagnetic radiation display a sequence of photon rings (demagnified and rotated copies of the direct image) which asymptotically approach a purely theoretical critical curve – the outline of the black hole photon shell. To a distant observer, these images appear dominated by the direct emission, which forms a ring whose diameter is primarily determined by the effective radius of the… 

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