Fig. 1

Different types of system (1a)–(1c) orbits according to the value of μ. In each panel, the cyan surface represents the x nullcline $S^0$ whose folds ${\mathcal{F}}^{\pm }$ are represented by red lines. a Attractive periodic orbit without small oscillations near the fold ${\mathcal{F}}^{-}$. This type of orbit is obtained for small values of μ. b Attractive MMO limit cycle with small oscillations near the fold ${\mathcal{F}}^{-}$. This type of orbit is obtained for an interval of μ values. c Orbit that, after a transient excursion in the phase portrait, tends to the attractive singular point of system (1a)–(1c) lying on the left sheet of $S^0$. This type of orbit is obtained for large value of μ. d is the zoom of the purple box of b and shows a magnified view of the small oscillations of the orbit