Imprints of Black Hole Shadows and Polarization Patterns of Various Thick Disks: Bumblebee gravity

Abstract

The main objective of this study is to explore the shadow and polarization patterns of a Kerr-Sen-like BH induced from Bumblebee gravity, which, among other alternative theories of gravity beyond Einstein gravity, stands out as a promising candidate for explaining certain high-energy astrophysical phenomena. Specifically, we would like to probe the influence of the rate of LSB parameter $\ell$ and the Bumblebee charge $Q$ on the resulting image morphology at $230\mathrm{GHz}$. We adopt a phenomenological RIAF-like model and an analytical BAAF disk model. Both models depict that the bright ring is encircled by two central dark regions, each of which gradually shrinks with increasing $\ell$. Consequently, frame-dragging gives rise to a pronounced brightness asymmetry, which is more enhanced with increasing $Q$. A notable feature in the anisotropic emission case is the emergence of a vertically stretched, elliptical ring structure. Compared with the RIAF framework, the bright ring in the BAAF disk images appears geometrically thinner, and the separation between the primary and higher-order images becomes more pronounced. Finally, the polarization patterns trace the brightness distribution and vary with both $\ell$ and $Q$, reflecting the spacetime structure. These results demonstrate that intensity and polarization in thick disk models provide probes of Kerr-Sen-like BHs and near-horizon accretion physics