GLOBAL BIFURCATIONS FROM THE CENTER OF MASS IN THE SITNIKOV PROBLEM

The Sitnikov problem is a restricted three body problem where the eccentricity of the primaries acts as a parameter. We find families of symmetric periodic solutions bifurcating from the equilibrium at the center of mass. These families admitaglobal continuation up to excentricity e = 1. The same techniques are applicable to the families obtained by continuation from the circular problem (e = 0). They lead to a refinement of a result obtained by J.Llibre and R.Ortega.