Polarized image of an equatorial emitting ring around a 4D Gauss–Bonnet black hole.

We have studied the polarized image of an equatorial emitting ring around a 4D Gauss–Bonnet black hole. Our results show that the effects of Gauss–Bonnet parameter on the polarized image depend on the magnetic field configuration, the observation inclination angle, and the fluid velocity. As the magnetic field lies in the equatorial plane, the observed polarization intensity increases monotonously with Gauss–Bonnet parameter in the low inclination angle case, and its monotonicity disappears in the case with high inclination angle. However, as the magnetic field is vertical to the equatorial plane, the polarization intensity is a monotonously increasing function of Gauss–Bonnet parameter in the high inclination angle case. The changes of the electric vector position angle with Gauss–Bonnet parameter in both cases are more complicated. We also probe the effects of Gauss–Bonnet parameter on the Strokes Q–U loops. [ABSTRACT FROM AUTHOR]