How extra charge and curvature reshape a black hole's glowing disk

Starting from a phenomenological deformation of the Kerr-Newman geometry, the authors compute how a higher-curvature parameter α and electric charge Q alter the key observables of a thin accretion disk. Increasing α moves the innermost stable circular orbit closer to the black hole and raises both radiation flux and disk temperature, while charge has the opposite effect, suppressing emission through electrostatic repulsion. The results suggest that disk spectra could discriminate between standard Kerr-Newman black holes and their higher-curvature cousins without requiring a specific modified-gravity theory.