# What is the escape velocity in the Kerr metric? [duplicate]

In the non-rotating Schwarzschild metric there is a straightforward expression for the escape velocity in the radial direction, defined from the point of view of a stationary observer at that radius, which is equivalent to the Newtonian result.

My questions are: is there an equivalent expression in the Kerr metric, how does it depend on the spin parameter, in which reference frame would that be defined and how does it depend on escape direction with respect to the spin axis?