Equatorial circular motion in a Kerr-like spacetime

TL;DR

This paper investigates how quadrupole deformations in a Kerr-like spacetime affect equatorial circular orbits of photons and particles, providing insights into stability and orbital characteristics around rotating compact objects.

Contribution

It introduces an approximate Kerr-like metric with quadrupole perturbation to analyze orbital effects, comparing results with Hartle-Thorne spacetime.

Findings

Quadrupole deformation influences photon sphere and ISCO.

Stability behavior is similar for co-rotating and counter-rotating particles.

Results align with Hartle-Thorne spacetime predictions.

Abstract

An study of the equatorial circular motion of photons and massive particles around a rotating compact body like a neutron star is presented. For this goal, we use an approximate Kerr-like metric with mass quadrupole as perturbation. The effect of this deformation on the photon sphere, and the innermost stable circular orbit, is determined via an effective potential. Furthermore, a stability anaysis is shown, where we observed the same behavior of the effective potential for co-rotating and counter-rotating particles. A comparison with the results for the innermost stable circular orbit obtained for the Hartle-Thorne spacetime is also presented.