Abstract: Magnetars are maximum stars. They carry the highest magnetic fields and emit the most energetic flares recorded. They have many other distinctive and puzzling features that defy explanation. We consider a model where the strong magnetic fields of magnetars arise from a high baryon density, magnetized core. In this framework magnetars are distinguished from pulsars by their higher masses and central density. For magnetars, as core densities exceed a threshold, the strong interaction induces a phase transition to a neutral pion condensate that aligns all magnetic moments. The core magnetic field is initially shielded by the ambient high conductivity plasma. With time the shielding currents dissipate transporting the core field out, first to the crust and then breaking through the crust to the surface of the star. Recent observations provide strong support for this model which accounts for several properties of magnetars and also and also enables us to identify new magnetars.
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