Motion of Spinning Particles around Electrically Charged Black Hole in Eddington-inspired Born-Infeld Gravity

TL;DR

This paper investigates the motion of spinning particles around charged black holes in EiBI gravity, revealing how the deviation parameter affects orbits and stability, with implications for observational constraints.

Contribution

It provides a detailed numerical analysis of spinning particle orbits in EiBI gravity, highlighting the influence of the deviation parameter on orbit stability and potential observational signatures.

Findings

Orbital eccentricity decreases with increasing deviation parameter 

Inner most stable circular orbit (ISCO) parameters vary non-monotonously with  for large spins

Two stable circular orbit regions may exist with different causality conditions

Abstract

A test particle possessing spin angular momentum moves along a non-geodesic path due to an additional spin-curvature force. We study the spinning test particle moving in the vicinity of the electrically charged black hole formation in Eddington-inspired Born-Infeld (EiBI) gravity. Through the numerical analysis of its effective potential and orbits, it is found that the orbital eccentricity reduces as the deviation parameter $\kappa$ increases. By comparing the orbits for the observed stars around Sagittarius A*, we conclude that the observed orbits with too large radii can not give a stringent constraint with acceptable magnitude. To dig out the potential observation effects of the relations between the orbits and parameter $\kappa$, we mainly focus on the orbits in the vicinity of black hole in this paper. The parameters of inner most stable circular orbit (ISCO) decrease monotonously with $\kappa$ when the spin angular momentum is small, however they change non-monotonously with $\kappa$ when the spin is large enough. Moreover, the spin dependences of ISCO parameters have similar behavior to that of Reissner-Nordstr\"om (RN) black hole. We analyze the causality of the circular orbits by using the superluminal constraint condition as well. As a result, two new parameter regions may emerge in case of large $\kappa$, where the particle has two stable circular orbits with one subluminal and the other superluminal.