Constraining Black Hole Mass and Charge from Shadow and Inner Shadow Morphology

We use ray-tracing techniques to investigate the morphology of the black hole shadow and inner shadow in the case of emission from thick and thin accretion disks in Schwarzchild and Reissner-Nordström spacetimes. Through these models we primarily study the effect of charge, observer inclination, and disk scaling ratio on the size and asymmetry of the inner shadow. We confirm that independent radii measurements of the shadow and inner shadow can constrain the mass and charge of a target Reissner-Nordström black hole with known viewing inclination. We also replicate these results to show similar constraints can be made on charge vs. inclination and charge vs. scale angle through the same process of independent measurements of the horizon radius and critical curve radius. We conclude that for sufficiently small scale angle, degeneracies between viewing inclination and scale angle can result in false constraints on the mass and charge.