Rastall gravity: accretion disk image in radiation fields context and visual transformations compared to Reissner-Nordstr"{o}m black holes

Abstract

Our study investigates the astronomical implications of Rastall gravity, particularly its behavior amidst a radiation field compared to Reissner-Nordstr"{o}m (RN) black holes. Our research delineates a crucial correlation between the dynamics of the accretion disk and the parameters Q and N_{\rm r}, which aptly reflect the influence of spacetime metrics on the disk's appearance. Elevated electric charge Q prompts contraction in the disk’s orbit due to enhanced gravitational effects, while higher N_{\rm r} values lead to outward expansion, influenced by the radiation field's attributes. Interestingly, the charged black holes surrounded by radiation fields display distinct visual disparities from RN black holes. Brightness decreases and expansion occurs within the accretion disk's innermost stable circular orbit with rising N_{\rm r} values. Our study also reveals the process by which the accretion disk transitions from a conventional disk-like structure to a hat-like form at different observation angles, with the redshift effect gradually intensifying. Moreover, the results of the Rastall gravity radiation field we consider are consistent with the constraints of the host galaxy's gravitational lensing on the Rastall gravity parameters, enhancing the consistency between theoretical predictions and actual observations.