Black hole shadows in M-theory scenarios

We study the shadows of four-dimensional black holes in M-theory inspired models. We first inspect the influence of M2-branes on such optical aspects for nonrotating solutions. In particular, we show that the M2-brane number can control the circular shadow size. This geometrical behavior is distorted for rotating solutions exhibiting cardioid shapes in certain moduli space regions. Implementing a rotation parameter, we analyze the geometrical shadow deformations. Among others, we recover the circular behaviors for a large M2-brane number. Investigating the energy emission rate at high energies, we find, in a well-defined approximation, that the associated peak decreases with the M2-brane number. Moreover, we investigate a possible connection with observations (from Event Horizon Telescope or future devices) from a particular M-theory compactification by deriving certain constraints on the M2-brane number in the light of the M87* observational parameters.

Automated summary

The study focuses on the shadows of four-dimensional black holes in M-theory inspired models, specifically examining the influence of M2-branes on nonrotating solutions and how the circular shadow size is controlled by the M2-brane number. The geometrical behavior is distorted for rotating solutions, showing cardioid shapes, with further analysis on shadow deformations as affected by a rotation parameter and energy emission rate at high energies. Investigations also provide constraints on the M2-brane number in relation to observations from the M87* parameters.