Publication date: Jan 2012
The appearance of corotating Keplerian discs orbiting Kerr superspinars
has been shown to be strongly dependent on the value of the superspinar
spin in both their shape and frequency shift profile, demonstrating
clear distinctions from the corotating discs around black holes.
However, it has to be modified in the innermost parts of the disc by the
self-illumination effect caused by the photons trapped in the strong
gravitational field near the superspinars with spin a < 9. Here we
demonstrate that self-illumination is irrelevant for counter-rotating
Keplerian discs orbiting in the field of all Kerr superspinars since
such discs are located at the regions where none of the radiated photons
can be trapped. Therefore, the results obtained by considering the
escaping photons only are quite relevant for the appearance of the
counter-rotating Keplerian discs orbiting Kerr superspinars. The
appearance and spectral continuum of such discs differ from those of
counter-rotating discs in the field of Kerr black holes. The differences
are of quantitative character except the existence of the disc images
located inside the image of the inner edge of the disc that are created
by photons reaching regions close to the surface of Kerr superspinars.
Their observational relevance is realistic in the near future for
accretion phenomena in the vicinity of Sgr A*.
Stuchlík, Zdeněk; Schee, Jan;