Catena integrates the orbits of an ensemble of stars using the chain-regularization method (Mikkola & Aarseth) with an embedded Runge-Kutta integration method of 9(8)th order (Prince & Dormand).
https://ui.adsabs.harvard.edu/abs/1993CeMDA..57..439M , https://ui.adsabs.harvard.edu/abs/1990CeMDA..47..375M , and https://ui.adsabs.harvard.edu/abs/2006MNRAS.373..295P