Evidence for planets orbiting the post‐common envelope binary NN Serpentis

From published and new mid‐eclipse times obtained between 1988 and 2010 we find long‐term eclipse time variations in the post‐common envelope eclipsing binary NN Ser. We find strong evidence for two circum‐binary planets in this system with orbital periods of Pc = 15.5 and Pd = 7.7 yrs, small eccentricities of ec≈0 and ed≈0.2 and lower mass limits of Mc sin ic = 6.9 and Mc sin ic = 2.2 MJup. The periods suggest that the planets are locked in a 2:1 resonance. A second solution with a 5:2 resonance and slightly modified planetary parameters results in a nearly equal reduced χ2. The progenitor system is estimated to consists of a ≈2 M⊙ primary and the present M dwarf secondary at ≈1.5 AU distance. The first generation formation of planets and their survival in the later evolutionary stages or the second generation formation in the common envelope shed new light on planet formation and evolution.