EHT observables as a tool to estimate parameters of supermassive black holes

Understand

The Event Horizon Telescope (EHT) collaboration unveiled event-horizon-scale images of the supermassive black holes (SMBHs) M87* and Sgr A*, revealing a dark brightness depression, namely the black hole shadow, whose shape and size may encode the parameters of the SMBHs, and the shadow is consistent with that of a Kerr black hole.

• It furnishes another encouraging tool to estimate black hole parameters and test theories of gravity in extreme regions near the event horizon.
• We propose a technique that uses EHT observables, the angular shadow diameter $d_{sh}$ and the axis ratio $\mathcal{D}_A$, to estimate the parameters associated with SMBHs, described by the Kerr metric.
• Unlike previous methods, our approach explicitly considers the uncertainties in the measurement of EHT observables.