Publication date: Mar 2019
Abstract:
We study the appearance of Keplerian accretion disks in order to
demonstrate the influence of the nonlinear electrodynamics (NED) on the
gravitational lensing and frequency shifting of the images of the
Keplerian disks. We focus our attention on the Bardeen black hole
backgrounds with magnetic charges that could be considered to be
acceptable solutions for the Einstein gravitational equations combined
with those representing an NED. Photons governing the appearance of the
Keplerian disks follow null geodesics of the effective geometry related
to the Bardeen spacetime. We compare the appearance governed by the
effective geometry to those governed by the spacetime geometry itself,
and to the appearance of Keplerian disks orbiting a related Reissner-
Nordstrom black hole spacetime. We demonstrate a clear and very strong
difference between the disk images determined by the effective geometry
and the others, both in the shape and (especially) in the frequency
mapping where it exhibits a difference of three orders.
Authors:
Schee, Jan; Stuchlík, Zdeněk;