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We have computed new stellar evolution models that include the effects ofrotation and magnetic torques under different hypothesis. The goal is to testif a single star can sustain in the envelope the rotational velocities neededfor the magneto hydrodynamical (MHD) simulations to shape bipolar PlanetaryNebulae (PNe) when the high mass-loss rates take place. Stellar evolutionmodels with main sequence masses of 2.5 and 5 Mo, and initial rotationalvelocities of 250 km/s have been followed all the way to the PNe formationphase. We find that stellar cores have to be spun down using magnetic torquesin order to reproduce the rotation rates observed for white dwarfs. During theasymptotic giant branch phase and beyond, the magnetic braking of the core hasa practically null effect in increasing the rotational velocity of the envelopesince the stellar angular momentum is removed efficiently by the wind. We have,as well, tested best possible case scenarios in rather non-physical contexts togive enough angular momentum to the envelope. We find that we cannot get theenvelope of a single star rotating at the speeds needed by the MHD simulationsto form bipolar PNe. We conclude that single stellar rotators are unlikely tobe the progenitors of bipolar PNe under the current MHD model paradigm.

Single Rotating Stars and the Formation of Bipolar Planetary Nebula