http://arxiv.org/abs/2304.02111
In this paper, we constrain the linear dark-matter-related parameter of a static spherically symmetric f (R) black hole spacetime regarding the observed angular diameters of M87* and Sgr A* from the EHT. We then investigate the light deflection angles inferred from direct analytical calculation of null geodesics and that obtained from the Gauss-Bonnet theorem. Assuming an optically thin accretion disk for the black hole and after discussing its properties, we conceive different emission profiles and investigate the shadow cast of this black hole when it is illuminated by the disk. Furthermore, we simulate the brightness of an infalling spherical accretion in the context of the silhouette imaging of the black hole. We find that, excluding some specific cases, the specific observed brightness of the accretion disk consists of the direct emission, rather than that for the lensing and photon rings. Furthermore, it is revealed that the linear dark parameter of the black hole has considerable effects on the size of the shadow and its brightness. The discussion is done both analytically and numerically, and ray-tracing methods are employed to generate proper visualizations
M. Fathi and N. Cruz
Thu, 6 Apr 23
41/76
Comments: 28 pages, 87 figures