Publication date: Apr 2013
Abstract:
String Theory suggests existence of primordial Kerr superspinars,
extremely compact objects with external spacetime described by the Kerr
naked singularity geometry. The primordial Kerr superspinars have to be
converted to a near-extreme black hole due to accretion, but they could
survive to the era of highly redshifted quasars. We study the shape of
the profiled spectral lines generated by radiating rings or the
innermost parts of Keplerian discs orbiting the Kerr superspinars.
Influence of the superspinar surface location on the profiled lines is
also considered. We demonstrate strong difference of the character of
the profiled lines generated by radiating rings for all values of the
superspinar spin and all values of the inclination angles of the
observer when compared to those generated in the field of Kerr black
holes. For small and mediate inclination angles there are large
quantitative differences in the extension and position of the lines. For
large inclination angles even strong qualitative difference appears as
the profiled lines have a clear doubled character. The smaller,
redshifted region of the profiled line is related to the photons
reaching the regions near the superspinar surface. Strong differences
are obtained also for profiled lines generated by the innermost parts of
Keplerian discs especially in the shape of the line. The influence of
the superspinar surface location is reflected in the intermediate parts
of the the profiled lines. The line profiles can give a clear signature
of the presence of a Kerr superspinar and in principle enable estimates
of its surface location since the signatures of the superspinar surface
location are of different character as those corresponding to the
presence of the black hole horizon.
Authors:
Schee, Jan; Stuchlík, Zdeněk;