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| Main Authors: | , |
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| Format: | Preprint |
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2026
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2605.26395 |
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| _version_ | 1866916046824275968 |
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| author | Bansawang, B. J. Surungan, Tasrief |
| author_facet | Bansawang, B. J. Surungan, Tasrief |
| contents | We study circular motion of charged test particles on the equatorial slice of a Taub--NUT black hole with Manko--Ruiz parameter $C$, immersed in a weak external magnetic field introduced via Wald's prescription. Because the Taub--NUT metric is not reflection-symmetric about the equator once $l\neq 0$, generic charged orbits lie on cones $x=\cosθ\neq 0$ rather than on the equatorial plane. We therefore analyse \emph{constrained} circular orbits obtained by imposing $x=\dot x=0$, and we exhibit in closed form the residual angular constraint that a fully self-consistent orbit would have to satisfy. Within this scope we derive the circularity and marginal-stability conditions and study how $B$ and $C$ shift the ISCO radius for prograde and retrograde branches. Increasing $B$ monotonically decreases $r_{\mathrm{ISCO}}$; the sign of the particle charge splits the two branches, with the ordering reversed between prograde and retrograde motion; and $C$ contributes only subleading corrections. The extension to self-consistent conical orbits is the natural direction for follow-up work. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_26395 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Equatorial Circular Motion of Charged Test Particles in a Weakly Magnetized Taub--NUT Background Bansawang, B. J. Surungan, Tasrief General Relativity and Quantum Cosmology We study circular motion of charged test particles on the equatorial slice of a Taub--NUT black hole with Manko--Ruiz parameter $C$, immersed in a weak external magnetic field introduced via Wald's prescription. Because the Taub--NUT metric is not reflection-symmetric about the equator once $l\neq 0$, generic charged orbits lie on cones $x=\cosθ\neq 0$ rather than on the equatorial plane. We therefore analyse \emph{constrained} circular orbits obtained by imposing $x=\dot x=0$, and we exhibit in closed form the residual angular constraint that a fully self-consistent orbit would have to satisfy. Within this scope we derive the circularity and marginal-stability conditions and study how $B$ and $C$ shift the ISCO radius for prograde and retrograde branches. Increasing $B$ monotonically decreases $r_{\mathrm{ISCO}}$; the sign of the particle charge splits the two branches, with the ordering reversed between prograde and retrograde motion; and $C$ contributes only subleading corrections. The extension to self-consistent conical orbits is the natural direction for follow-up work. |
| title | Equatorial Circular Motion of Charged Test Particles in a Weakly Magnetized Taub--NUT Background |
| topic | General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2605.26395 |