Observational Signatures of Rotating Ayón-Beato-García Black Holes: Shadows, Accretion Disks and Images

Abstract

We investigate the shadows, accretion disks, and observational images of rotating Ayón-Beato--Garc\'ıa (ABG) black holes with mass $M$, spin $a$, and nonlinear-electrodynamics (NLED) charge parameter $\zeta$, treating photons as neutral test particles on null geodesics of the background metric so as to obtain the purely geometric shadow. The shadow shrinks with increasing $\zeta$ and develops a ``D''-shaped morphology for near-extremal spin. The thermal disk properties follow from the Novikov--Thorne model with inner edge at the innermost stable circular orbit (ISCO), whereas the images use a separate, phenomenological optically thin emission model extending to the horizon. The image asymmetry and redshift maps depend strongly on $(a,\zeta )$ and the inclination. Comparing the geometric shadow diameters with Event Horizon Telescope observations of M87${}^{\ast }$ and Sgr A${}^{\ast }$ gives the indicative estimates $\zeta \lesssim 0.21M$ and $\zeta \lesssim 0.43M$, respectively; since $\zeta$ characterizes each black hole individually, these are quoted separately rather than combined, and the Kerr limit $\zeta =0$ remains fully consistent with both.

16 pages, 13 figures