Of Wolf-Rayet central stars and common envelopes

Although single star evolutionary calculations have recently succeeded in reproducing the composition of the hydrogen-deficient Wolf-Rayet (WR) central stars of planetary nebulae, it is clear from the latest infrared observations that a new perspective has to be adopted: the simultaneous presence of carbon- and oxygen-rich dust, while being a rare phenomenon for H-rich central stars, is found around the vast majority of cool WR central stars. De Marco & Soker (2002) proposed that the majority of WR central stars are the result of a merger with a low-mass companion during the asymptotic giant branch (AGB) phase. In this work, we partly test this speculative suggestion by 3-dimensional hydrodynamical models, which simulate the common envelope phase between 0.1 and 0.2M_⊙ companions and an AGB star at the rst and tenth thermal pulse.