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

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.
Comment: 14 pages, 29 figures