Iterative refinement for pr
When the dynamics ends because of dprst/dt = 0, the position of the peak of prst is recomputed with an iterative refinement procedure, similar to what is done for the orbital frequency. Relevant only for some cases with q>40 and chi1~0.99 where the Kerr ISCO is after the end of the dynamics, and the stopping condition is dprst/dt = 0.