Precession of spherical orbits for the spacetime without $\mathbb{Z}_2$ symmetry induced by NUT charge

TL;DR

This paper investigates how a nonzero NUT charge affects the precession of spherical orbits in Kerr-Taub-NUT spacetime, linking theoretical predictions to black hole jet precession observations, especially in M87*.

Contribution

It provides a detailed analysis of geodesic precession in NUT spacetime and constrains black hole parameters using jet precession data, highlighting the effects of NUT charge and spin.

Findings

Precession increases with NUT charge and spin.

Low spin and large NUT charge regions are excluded by observations.

Jet precession cannot determine the sign of NUT charge.

Abstract

Astrophysical evidence has hinted at the existence of a nonzero NUT charge, which breaks the $\mathbb{Z}_2$ symmetry of spacetime and induces novel features in geodesics. In this work, we investigate the Lense-Thirring precession of the spherical orbits in the Kerr-Taub-NUT spacetime, with particular emphasis on its connection to recent observations of black hole jet precession. We analyze the reflection symmetry breaking in trajectories of the spherical orbits and extract their precession angular velocity. It is worth noting that in the absence of spin, the spherical orbits reduce to tilted circular orbits without precession, whereas for nonzero spin, the precession angular velocity increases with the absolute value of the NUT charge. We then model the motion of particles near the warp radius of a tilted accretion disk using the spherical orbits and constrain the black hole parameter space based on the observed jet precession of M87*. The results indicate that regions with low spin and large NUT charge were excluded, and that the jet precession measurements cannot distinguish the sign of the NUT charge. The excluded region is larger for retrograde accretion disks than for prograde ones. We also find that this observation do not allow a clear distinction between black holes and naked singularities. Moreover, we also explore how black hole parameters influence the structure of accretion disk. These results have important theoretical and astronomical significance for us to deeply understand NUT space-time.