Panel a: resonant radii of Ep models calculated in Kerr spacetimes. The enlarged area emphasizes a region close to a = 1 where each a(r_p:q) function exhibits both a local minimum and a local maximum. Global minima of r_p:q(a) functions are denoted by circles. Panel b: detailed view of the behaviour of the r_3:1(a) relation for a ≈ 1. The global minimum of r_3:1 is not shown since it occurs only for a higher value of spin, a_3:1 = 1.08471.