Shadow of axisymmetric, stationary, and asymptotically flat black holes in the presence of plasma

JAVIER BADÍA; ERNESTO F. EIROA

Physical Review D

Amer Physical Soc

Lugar: New York; Año: 2021 vol. 104 p. 84055 - 84055

2470-0010

We study the shadow produced by a class of rotating black holes surrounded by plasma. The metric for these black holes arises by applying the Newman-Janis algorithm to a family of spherically symmetric spacetimes, which includes several well-known geometries as special cases. We derive a general expression for the shape of the shadow in the case that the plasma frequency leads to a separable Hamilton-Jacobi equation for light. We present two examples in which we obtain the shadow contours and the observables resulting from them. In one, we analyze Kerr-Newman-like geometries, including braneworld and Horndeski gravity black holes, while in the other, we consider scalar-tensor 4D Einstein-Gauss-Bonnet gravity spacetimes. In both cases, we find that the presence of plasma leads to a smaller and less deformed shadow.