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Astron. Astrophys. 331, 1143-1146 (1998)

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Research Note

On the runaway instability of relativistic tori *

Marek A. Abramowicz 1, 3, 4, Vladimír Karas 2 and Antonio Lanza 3

1 Department of Astronomy and Astrophysics, Göteborg University and Chalmers University of Technology, S-412 96 Göteborg, Sweden (marek@tfa.fy.chalmers.se)
2 Astronomical Institute, Charles University, Faculty of Mathematics and Physics, V Holeovikách 2, CZ-180 00 Praha, Czech Republic (karas@mbox.cesnet.cz)
3 Scuola Internazionale Superiore di Studi Avanzati, Via Beirut 2-4, I-34 014 Trieste, Italy (lanza@sissa.it)
4 International Centre for Theoretical Physics, Strada Costiera 11, I-34 014 Trieste, Italy

Received 15 September 1997 / Accepted 30 October 1997

Abstract

We further investigate the runaway instability of relativistic tori around black holes assuming a power law distribution of the specific angular momentum. We neglect the self-gravity of the torus; thus the gravitational field of the system is determined by the central rotating black hole alone (the Kerr geometry). We find that for any positive (i.e. consistent with the local Rayleigh stability condition) power law index of the angular momentum distribution, the tori are always runaway stable for a sufficiently large spin of the black hole. However, before concluding that some (astrophysically realistic) tori could indeed be runaway stable, one should include, in full general relativity, the destabilizing effect of self-gravity.

Key words: accretion: accretion-discs – black hole physics – instabilities

* Work prepared during The Annual Nordic-Trieste Astrophysics Workshop (ICTP, Trieste 1997)

Send offprint requests to: V. Karas

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© European Southern Observatory (ESO) 1998

Online publication: March 3, 1998
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