Motion of test particle in rotating boson star

TL;DR

This study explores the motion of test particles around rotating boson stars, revealing how their orbits and relativistic effects vary with rotation, and discusses potential observable signatures in galactic centers.

Contribution

It provides a detailed analysis of test particle geodesics in rotating boson star spacetimes, highlighting how rotation influences orbital dynamics and potential astrophysical observations.

Findings

Test particles can remain longer in the central region as boson stars become highly relativistic.

Significant Lense-Thirring effects are observed in rapidly rotating boson stars.

Orbital characteristics differ from those around black holes, suggesting possible observational distinctions.

Abstract

Motion of a test particle plays an important role in understanding the properties of a spacetime. As a new type of the strong gravity system, boson stars could mimic black holes located at the center of galaxies. Studying the motion of a test particle in the spacetime of a rotating boson star will provide the astrophysical observable effects if a boson star is located at the center of a galaxy. In this paper, we investigate the timelike geodesic of a test particle in the background of a rotating boson star with angular number $m=(1, 2, 3)$. With the change of angular number and frequency, a rotating boson star will transform from the low rotating state to the highly relativistic rapidly rotating state, the corresponding Lense-Thirring effects will be more and more significant and it should be studied in detail. By solving the four-velocity of a test particle and integrating the geodesics, we investigate the bound orbits with a zero and nonzero angular momentum. We find that a test particle can stay more longer time in the central region of a boson star when the boson star becomes from low rotating state to highly relativistic rotating state. Comparing the periapse values of the orbits obtained in rotating boson stars and the corresponding orbits of the observed stars orbiting Sagittarius $A^*$, we discuss the possible observable effects of the astrophysical boson star in the Galactic center.