Modification of photon trapping orbits as a diagnostic of non-Kerr spacetimes

@article{Glampedakis2019ModificationOP,
  title={Modification of photon trapping orbits as a diagnostic of non-Kerr spacetimes},
  author={Kostas Glampedakis and George Pappas},
  journal={Physical Review D},
  year={2019}
}
Photon circular orbits, an extreme case of light deflection, are among the hallmarks of black holes and are known to play a central role in a variety of phenomena related to these extreme objects. The very existence of such orbits when motion is not confined in the equatorial plane, i.e. spherical orbits, is indeed a special property of the separable Kerr metric and may not occur, for instance, in the spacetime of other more speculative ultracompact objects. In this paper we consider a general… 
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