Extended bodies in a Kerr spacetime: exploring the role of a general quadrupole tensor

TL;DR

This paper investigates how a general quadrupole tensor influences the motion of extended bodies in Kerr spacetime, revealing effects like spiraling and spin-flip phenomena through numerical analysis.

Contribution

It extends previous studies by including the full set of quadrupole tensor components, highlighting magnetic effects on orbital dynamics in Kerr spacetime.

Findings

Magnetic-type quadrupole components cause enhanced spiraling behavior.

General quadrupole tensor affects spin-flip-like phenomena.

Model validity limits are explicitly discussed.

Abstract

The equatorial motion of extended bodies in a Kerr spacetime is investigated in the framework of the Mathisson-Papapetrou-Dixon model, including the full set of effective components of the quadrupole tensor. The numerical integration of the associated equations shows the specific role of the mass and current quadrupole moment components. While most of the literature on this topic is limited to spin-induced (purely electric) quadrupole tensor, the present analysis highlights the effect of a completely general quadrupole tensor on the dynamics. The contribution of the magnetic-type components is indeed related to a number of interesting features, e.g., enhanced inward/outward spiraling behavior of the orbit and spin-flip-like effects, which may have observational counterparts. Finally, the validity limit of the Mathisson-Papapetrou-Dixon model is also discussed through explicit examples.