Zdenek Stuchlik, Jan Schee


We investigate possible signatures of a Kerr naked singularity (superspinar) in various observational phenomena. It has been shown that Kerr naked singularities (superspinars) have to be efficiently converted to a black hole due to accretion from Keplerian discs. In the final stages of the conversion process the near-extreme Kerr naked singularities (superspinars) provide a variety of extraordinary physical phenomena. Such superspinning Kerr geometries can serve as an efficient accelerator for extremely high-energy collisions, enabling a direct and clear demonstration of the outcomes of the collision processes. We shall discuss the efficiency and the visibility of the ultra-highenergy collisions in the deepest parts of the gravitational well of superspinning near-extreme Kerr geometries for the whole variety of particles freely falling from infinity. We demonstrate that ultrahigh-energy processes can be obtained with no fine tuning of the motion constants and the products of
the collision can escape to infinity with efficiency substantially higher than in the case of near-extreme black holes. Such phenomena influence the radiative processes taking place in the accretion disc, and together with the particular generated geometry they influence the observed radiation field. Here we
assume the “geometrical” influence of a Kerr naked singularity on the spectral line profiles of radiation emitted by monochromatically and isotropically radiating point sources forming a Keplerian ring or disc around such a compact object. We have found that the profiled spectral line of the radiating
Keplerian ring can be split into two parts because there is no event horizon in the naked singularity spacetimes. The profiled lines generated by Keplerian discs are qualitatively different for a Kerr naked singularity and black hole spacetimes broadened near the inner edge of a Keplerian disc.


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ISSN 1210-2709 (Print)
ISSN 1805-2363 (Online)
Published by the Czech Technical University in Prague