EDP Sciences
Free access
Volume 437, Number 3, July III 2005
Page(s) 775 - 788
Section Astrophysical processes
DOI http://dx.doi.org/10.1051/0004-6361:20052825

A&A 437, 775-788 (2005)
DOI: 10.1051/0004-6361:20052825

Radial and vertical epicyclic frequencies of Keplerian motion in the field of Kerr naked singularities

Comparison with the black hole case and possible instability of naked-singularity accretion discs
G. Török and Z. Stuchlík

Institute of Physics, Faculty of Philosophy and Science, Silesian University in Opava, Bezrucovo nám. 13, 746 01 Opava, Czech Republic
    e-mail: stu10uf@fpf.slu.cz; terek@volny.cz

(Received 6 February 2005 / Accepted 8 March 2005)

Relativistic Keplerian orbital frequency ( $\nu_{\mathrm{K}}$) and related epicyclic frequencies (radial $\nu_{\mathrm{r}}$, vertical $\nu_{\theta}$) play an important role in the physics of accretion discs orbiting Kerr black holes - quasiperiodic oscillations observed in microquasars can be explained by associated resonant or trapping effects. Because of growing theoretical evidence of the possible existence of naked singularities, we discuss the behaviour of the fundamenal orbital frequencies for Keplerian motion in the field of Kerr naked singularities, primarily in order to find phenomena that could observationally distinguish a hypothetical naked singularity from black holes. Some astrophysically important consequences are sketched, namely the existence of strong resonant frequency for all Kerr naked singularities, with radial and vertical epicyclic frequencies equal and given by the relation $\omega_\mathrm{sr}\,$= $\,\,a^{-2}\sqrt {a^2-1}\,(a^2+1 )^{-1}$.

Key words: black holes physics -- X-rays: general

© ESO 2005

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access.

An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account.
    In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.