Shadows and deflection angle of charged and slowly rotating black holes in Einstein-Æther theory

In this paper, we study the shadow cast by two types of charged and slowly rotating black holes in the Einstein-Æther theory of gravity. These two types of black holes correspond to two specific combinations of the coupling constants of the æther field, i.e., c14=0 but c123≠0 for the first type and c123=0 for the second type. For both types of black holes, in addition to the mass and charge of the black holes, we show that the presence of the æther field can also affect the size of the shadow. For the first type of black hole, it is shown that the shadow size increases with the parameter c13, while for the second type of black hole, the shadow size still increases with c13 but decreases with the parameter c14. With these properties of the æther parameters, we also discuss the observational constraints on these parameters by using the data of the first black hole image by the Event Horizon Telescope. In addition, we also explore the effect of the æther field on the deflection angle of light and the time delay by using the Gauss-Bonnet theorem. It is shown that, for a specific combination c123=0, the deflection angle/time delay is slightly affected by the æther parameter c13 at the leading order.