Regularizing Parameterized Black Hole Spacetimes with Kerr Symmetries (II): Observables

Parameterized Kerr spacetimes allow us to test the nature of black holes in model-independent ways. In the series of talks, we focus on the parameterized spacetime preserving Killing symmetries of a Kerr spacetime. In this second talk, we will show from the metric one can derive expressions describing physical observables of black holes. We will discuss the gravitational-wave ringdown frequencies and the shapes of black hole shadows for several example deviation parameters.