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Inner-most stable circular orbits in extremal and non-extremal Kerr-Taub-NUT spacetimes

Authors
  • Chakraborty, Chandrachur
Type
Published Article
Publication Date
Jan 29, 2014
Submission Date
Jul 17, 2013
Identifiers
DOI: 10.1140/epjc/s10052-014-2759-9
Source
arXiv
License
Yellow
External links

Abstract

We study causal geodesics in the equatorial plane of the extremal Kerr-Taub-NUT spacetime, focusing on the Innermost Stable Circular Orbit (ISCO),and compare its behaviour with extant results for the ISCO in the extremal Kerr spacetime. Calculation of the radii of the direct ISCO, its Kepler frequency, and rotational velocity show that the ISCO coincides with the horizon in the exactly extremal situation. We also study geodesics in the strong {\it non}-extremal limit, i.e., in the limit of vanishing Kerr parameter (i.e., for Taub-NUT and massless Taub-NUT spacetimes as special cases of this spacetime). It is shown that the radius of the direct ISCO increases with NUT charge in Taub-NUT spacetime. As a corollary, it is shown that there is no stable circular orbit in massless NUT spacetimes for timelike geodesics.

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